I don't like to feed hatchlings in the viv for this reason- they go off and forget they even had a mouse.
I'd feed the baby in a deli cup, and I'd start off with a boiled pink, slit. So you place a frozen pink in a cup (that you can pour boiling water into), boil water, pour it over the pink, remove the pink, cut several slits down its back, and serve piping hot. I'd feed in the evening, cover the deli cup with a towel, and not peek for two hours. If the snake hasn't fed, reheat and leave in the deli overnight.
I have a list with a TON of feeding tricks down in my personal forum. Boiled works really well.