The sprint button in Seeker vs Hider on Roblox appears to be Left Joystick on console, and the game listing also shows Sprint as a control. For PC, the listing shows C/X for crouch/stand and R/M1 , F/M1 , M1 , M2 , and P , but it does not clearly show a dedicated sprint key in the excerpt I found.

If you’re on mobile, sprint may be handled differently or by a UI button depending on the device and version, so the safest move is to check the in- game controls screen.