Oh, he's so cute! And yes, that's what I love most about rat snakes- they're very aware. Are you feeding him live? (You should, if he's going back outside in the spring.) I'm glad you found him in time, & before your cats did any damage.
BTW, I'm glad I'm not the only one that worries about what one of my snakes might catch while at a vet's office. Most likely your snake is just slow at going into his next shed? Probably nothing to worry about.