Don't panic... rats tend to like to explore Ben might have wanted to look around the house a bit, or something may have panicked him... Many rats panic easily and just bolt off in any direction.
If you feel you are making progress in your relationship with your rats, you most probably are. That doesn't mean some rats aren't still flighty. Our girl Misty has just decided she doesn't want to be manhandled or put into her cage... she will climb all over me and tunnel under my clothes, but whenever I try and hold or restrain her she becomes a wriggling slippery little rat and she'll jump right off of me... usually she'll run right back to me to play fight me some more, but for now calmly being held isn't in her repertoire. She knows it's past her bedtime and I know I'm not going to see her until tomorrow evening when she wants to play again...
This is just a phase she's going through, we have a wonderful relationship and once she gets the rebel out of her system she'll be fine.... she'll actually nap under my desk near my feet when I don't know she is there... She's a good girl, but for now she's also rebelling against authority like every good teenager does.
Don't let Ben's behavior get you all twisted up, maybe there is still progress to be made in your relationship, or maybe he panics easily, or maybe he just wanted to explore... no matter which one is correct, it's no big deal and you will work through it... for now just stuff some old towels under your door and keep working with him.
Best luck.