diff --git a/Sources/Swiftly/Install.swift b/Sources/Swiftly/Install.swift
index d7eb33f1..abb85361 100644
--- a/Sources/Swiftly/Install.swift
+++ b/Sources/Swiftly/Install.swift
@@ -159,6 +159,12 @@ struct Install: SwiftlyCommand {
             let swiftlyBinDirContents =
                 (try? await fs.ls(atPath: swiftlyBinDir)) ?? [String]()
             let toolchainBinDir = try await Swiftly.currentPlatform.findToolchainBinDir(ctx, version)
+            guard try await fs.exists(atPath: toolchainBinDir) else {
+                throw SwiftlyError(
+                    message:
+                    "Toolchain \(version) could not be located in \(toolchainBinDir). You can try `swiftly uninstall \(version)` to uninstall it and then `swiftly install \(version)` to install it again."
+                )
+            }
             let toolchainBinDirContents = try await fs.ls(atPath: toolchainBinDir)
 
             var existingProxies: [String] = []
@@ -250,18 +256,26 @@ struct Install: SwiftlyCommand {
         assumeYes: Bool,
         progressFile: FilePath? = nil
     ) async throws -> (postInstall: String?, pathChanged: Bool) {
-        guard !config.installedToolchains.contains(version) else {
-            let installInfo = InstallInfo(
-                version: version, alreadyInstalled: true
-            )
-            let pathChanged = if useInstalledToolchain {
-                try await Use.execute(ctx, version, globalDefault: false, verbose: verbose, &config)
-            } else {
-                false
+        if config.installedToolchains.contains(version) {
+            let toolchainBinDir = try await Swiftly.currentPlatform.findToolchainBinDir(ctx, version)
+
+            if try await fs.exists(atPath: toolchainBinDir) {
+                let installInfo = InstallInfo(
+                    version: version, alreadyInstalled: true
+                )
+                let pathChanged = if useInstalledToolchain {
+                    try await Use.execute(ctx, version, globalDefault: false, verbose: verbose, &config)
+                } else {
+                    false
+                }
+
+                try await ctx.output(installInfo)
+                return (nil, pathChanged)
             }
 
-            try await ctx.output(installInfo)
-            return (nil, pathChanged)
+            await ctx.message(
+                "Toolchain \(version) can no longer be located in \(toolchainBinDir). You can try `swiftly uninstall \(version.name); swiftly install \(version.name)` to reinstall it."
+            )
         }
 
         // Ensure the system is set up correctly before downloading it. Problems that prevent installation
diff --git a/Tests/SwiftlyTests/InstallTests.swift b/Tests/SwiftlyTests/InstallTests.swift
index 28b60331..43cf4063 100644
--- a/Tests/SwiftlyTests/InstallTests.swift
+++ b/Tests/SwiftlyTests/InstallTests.swift
@@ -239,6 +239,26 @@ import Testing
         #expect(before == after)
     }
 
+    /// Tests that a toolchain that is installed according to the config, but missing from disk, is installed again.
+    @Test(.testHomeMockedToolchain()) func installToolchainMissingFromDisk() async throws {
+        try await SwiftlyTests.runCommand(Install.self, ["install", ToolchainVersion.newStable.name, "--post-install-file=\(fs.mktemp())"])
+
+        try await fs.remove(atPath: Swiftly.currentPlatform.findToolchainLocation(SwiftlyTests.ctx, .newStable))
+
+        let output = try await SwiftlyTests.runWithMockedIO(
+            Install.self, ["install", ToolchainVersion.newStable.name, "--post-install-file=\(fs.mktemp())", "--format", "json"], format: .json
+        )
+
+        let installInfo = try JSONDecoder().decode(
+            InstallInfo.self,
+            from: output[0].data(using: .utf8)!
+        )
+
+        #expect(installInfo.alreadyInstalled == false)
+
+        try await SwiftlyTests.validateInstalledToolchains([.newStable], description: "install a toolchain missing from disk")
+    }
+
     /// Verify that the installed toolchain will be used if no toolchains currently are installed.
     @Test(.testHomeMockedToolchain()) func installUsesFirstToolchain() async throws {
         let config = try await Config.load()
diff --git a/Tests/SwiftlyTests/UseTests.swift b/Tests/SwiftlyTests/UseTests.swift
index 70687a4f..ef497647 100644
--- a/Tests/SwiftlyTests/UseTests.swift
+++ b/Tests/SwiftlyTests/UseTests.swift
@@ -244,6 +244,16 @@ import Testing
         )
     }
 
+    /// Tests that the `use` command reports a toolchain that is installed according to the config, but missing from disk.
+    @Test(.mockedSwiftlyVersion(), .mockHomeToolchains(toolchains: [.newStable])) func useToolchainMissingFromDisk() async throws {
+        try "swiftly binary".write(to: Swiftly.currentPlatform.swiftlyBinDir(SwiftlyTests.ctx) / "swiftly", atomically: true)
+        try await fs.remove(atPath: Swiftly.currentPlatform.findToolchainLocation(SwiftlyTests.ctx, .newStable))
+
+        await #expect(throws: SwiftlyError.self) {
+            try await SwiftlyTests.runCommand(Use.self, ["use", ToolchainVersion.newStable.name])
+        }
+    }
+
     /// Tests that the `use` command works with all the installed toolchains in this test harness.
     @Test(.mockedSwiftlyVersion(), .mockHomeToolchains()) func useAll() async throws {
         let config = try await Config.load()