diff --git a/nise-backend/src/main/kotlin/com/nisemoe/nise/controller/UserDetailsController.kt b/nise-backend/src/main/kotlin/com/nisemoe/nise/controller/UserDetailsController.kt
index 9c31733..28103e1 100644
--- a/nise-backend/src/main/kotlin/com/nisemoe/nise/controller/UserDetailsController.kt
+++ b/nise-backend/src/main/kotlin/com/nisemoe/nise/controller/UserDetailsController.kt
@@ -2,22 +2,15 @@ package com.nisemoe.nise.controller
 
 import com.nisemoe.generated.tables.references.SCORES
 import com.nisemoe.nise.SimilarReplayEntry
-import com.nisemoe.nise.database.ScoreService
 import com.nisemoe.nise.SuspiciousScoreEntry
 import com.nisemoe.nise.UserDetails
 import com.nisemoe.nise.UserQueueDetails
+import com.nisemoe.nise.database.ScoreService
 import com.nisemoe.nise.database.UserService
 import com.nisemoe.nise.service.AuthService
 import com.nisemoe.nise.service.UpdateUserQueueService
 import org.springframework.http.ResponseEntity
-import org.springframework.web.bind.annotation.GetMapping
-import org.springframework.web.bind.annotation.PathVariable
-import org.springframework.web.bind.annotation.PostMapping
-import org.springframework.web.bind.annotation.RequestBody
-import org.springframework.web.bind.annotation.RestController
-import java.time.LocalDateTime
-import java.time.OffsetDateTime
-import java.time.ZoneOffset
+import org.springframework.web.bind.annotation.*
 
 @RestController
 class UserDetailsController(
@@ -41,6 +34,10 @@ class UserDetailsController(
 
     @PostMapping("user-queue")
     fun addUserToQueue(@RequestBody request: UserQueueRequest): ResponseEntity<Unit> {
+        // Check if the user_id currently exists
+        this.userService.getUserById(userId = request.userId)
+            ?: return ResponseEntity.notFound().build()
+
         val userQueueDetails = this.userQueueService.getUserQueueDetails(request.userId)
         if(!userQueueDetails.canUpdate)
             return ResponseEntity.badRequest().build()
diff --git a/nise-backend/src/main/kotlin/com/nisemoe/nise/database/UserService.kt b/nise-backend/src/main/kotlin/com/nisemoe/nise/database/UserService.kt
index 8fea58e..4388db6 100644
--- a/nise-backend/src/main/kotlin/com/nisemoe/nise/database/UserService.kt
+++ b/nise-backend/src/main/kotlin/com/nisemoe/nise/database/UserService.kt
@@ -45,6 +45,35 @@ class UserService(
         return dslContext.fetchCount(SCORES, SCORES.USER_ID.eq(userId))
     }
 
+    fun getUserById(userId: Long): UserDetails? {
+        val user = dslContext.selectFrom(USERS)
+            .where(USERS.USER_ID.eq(userId))
+            .fetchOneInto(UsersRecord::class.java)
+
+        if (user != null) {
+            return UserDetails(
+                user.userId!!,
+                user.username!!,
+                user.rank,
+                user.ppRaw,
+                user.joinDate?.let { Format.formatLocalDateTime(it) },
+                user.secondsPlayed,
+                user.country,
+                user.countryRank,
+                user.playcount
+            )
+        }
+
+        // The database does NOT have the user; we will now use the osu!api
+        val apiUser = this.osuApi.getUserProfile(userId = userId.toString(), mode = "osu", key = "id")
+            ?: return null
+
+        // Persist to database
+        insertApiUser(apiUser)
+
+        return this.mapUserToDatabase(apiUser)
+    }
+
     fun getUserDetails(username: String): UserDetails? {
         val user = dslContext.selectFrom(USERS)
             .where(USERS.USERNAME.equalIgnoreCase(username.lowercase()))