They don't always go back into their hide after eating ... Most of mine do but I have a normal male (my go to guy) that will sit at the front of his tub afterwards and watch as I feed everyone else hoping that someone doesn't eat so he gets the leftovers lol (hes a hoss at a lil over 5ft.) .... Out of curiosity how big is your snake? Is it possible he was looking for another mouse? I only feed rats to my balls, so a mouse hopper/young adult almost sounds to me like it might be looking for another unless it's a really young snake .. then this size feeder would probably suffice. But as long as the lump moved down it's body and to it's stomach I see no reason you should worry ... Probably just being explorative