Oh geez, I never even considered this. . . That's incredibly unfortunate. I'm so sorry! I wish they would, like, stay in a sort of . . . purgatory/pending den in the event that that happened. Like, a special little holding area in the Campaign where you have a timer or something to claim the wolf by so you're able to make room and avoid losing them.
It really was unfortunate, but ever since I have taken care to always have one o two free slots just in case. And I've had a couple WWs join me. So it's all good. It was ... a learning experience for sure lol