My king snake came back! - Am I doing this right..?

[VikingzTV]

So my Mexican black kingsnake (Thor is his name) SOMEHOW escaped his enclosure last November (2015); I have no clue how he managed to do it as I have 4 locks on each side of the lid to his enclosure and it is about a foot or so high (I do have a TON of aspen bedding in there though because he LOVES to burrow in it). I looked everywhere in my basement, turned over the couch, look inside drawers, behind them, etc. Anyways I was on my computer (his enclosure is beside the PC) the other day when i felt a tap on my foot, and there he was, staring straight back at me. You'd think it was one of those cliche 90's/90's movies where we run (slither..?) into each others arms in slow motion.. I was SO happy my snake was back and I immediately put him into the new enclosure I bought and set up for him in his absence. He seemed to enjoy it (it is much bigger than the last though he is a fairly small snake). I filled his water dish and he sat there for a solid 5 minutes gulping down water. Now, I am not entirely sure if this was the right move, but I immediately thawed out a mouse for him and set it by his hide for an hour or so and went away, he hadn't eaten it.. So I tried it again the following day, same reaction. He just wasn't interested, I set it right beside him and he would just look at it for a while then slither away. I just set up a smaller enclosure for him, I thought maybe the size of the new one made him feel a little overwhelmed. I'll try feeding him later today as I gave him a break yesterday to get used to his new surroundings. Oddly, he doesn't seem to have lost any weight.. I am 90% sure we don't have rodents in our basement, maybe he brumated somewhere? Thought I'd just ask if I have taken the proper steps to get him back to his normal routine. Everything as of now is the exact setup as before he got out, tempurature, humidity, etc. Any help on this is appreciated! Thanks!

Edit: He is just over one year old now; if that makes any difference.