Warden doesnt despawn

Hi, I explored an ancient city in a survival world which was using this server, and I accidently spawned a Warden, So I ran away, and I thought that the warden had despawned, because I ran into another shrieker which spawned another warden. and then that warden killed me. 2 days later I return to that same ancient city to find the first warden had not despawned, AND the SECOND warden had also not despawned and I SPAWNED ANOTHER ON MY WAY THEIR. And you can only have 1 warden spawn per time soo Idk what to do can someone please help me find a fix, otherwise Ill have to spend ages finding another ancient city