Before I started breeding my own, I would go to the pet store every week to get feeders. If I had a refusal, I had a 10gallon set up to house and feed the refused meal until the next week. The problem is that rat pups and fuzzies aren't weaned yet and won't survive a week away from the mom. Your best options would be to either work out a deal with the pet store to return refused feeders for credit, or humanely kill the rodent and freeze it so it doesn't slowly starve to death.