I'm with everyone else that you won't have a problem getting the log book back, no confrontation required.
A good reason to not agree to have the school hold the books in the future, however, is what would happen were the school to declare bankruptcy? Then you'd be SOL, at least until you managed to get it back from whomever is liquidating the company. In that case, since there's no intrinsic monetary value to the log book I would expect it to eventually be turned over to you, but I can't say that for certain, and I don't know if they would be able to auction it off, with you as the only reasonable bidder. Mybe one of the lawyers could speak to that scenario.
Reiterating, though for the OP, he should have no problem getting the log book back in his situation.