I wouldn't be leaving a mouse of any size other then a pinky in his cage unatended. I learned this the hard way with my first boa, and had to apply cream to his wounds, and antibiotics through his mouth for months to patch him up.(the mouse ate a few nice holes in him)
One thing i would try is tou leave a mouse near the entrance of his hide, i found this works with my snakes. They feel more secure striking inside tight dark places where there safe from us humans.
When did you buy him? How much time did you allow him to adjust to his enclosure. If you bought him put him in his enclosure, then handled him/tried to feed him that day and continued this process then you upset his adjustment time. I always alow at least a week for adjustment with absolutely no interference. When i first put a new snake in an enclosure i shut it and thats it for 7 to ten days. The only case in which i bother them at all is if i HAVE to clean the waterbowl. Then around ten days later they should take food fine, if you didnt alow his to adjust then you might have some problems. If you handled him/tried to feed him before he was completely adjusted then he could be stressed, and might stay stressed. My recommendation would to force feed him one more time, give him a big meal, bigger then usual but not huge. Then put him in his enclosure with a nice sized full water bowl that you wont have to change that often and leave him be for about two to three weeks. Don't so much as walk by the cage if you don't have to. Only change the waterbowl when its really low or dirty and make sure his temperatures dont go below 82 degrees ferenheit.
Then offer him a live mouse of appropriate size, he should eat. I've noticed snakes can be quite spoiled... you can offer them food at every turn and theyll turn it down, but if they get hungry enough they WILL eat. Just make sure you feed him the big meal, provide him with water, and leave him be and hell come around. As long as he goes into this cycle with a full stomache and is able to hydrate as he pleases, not feeding him for a couple weeks shouldnt hurt.
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2.3 Bearded Dragons
1.0 Pastel Ball Pythons (NERD Line)
0.0.1 Water Monitors
1.1 Pastel Red Tailed boa Het. for Albino
1.1 Yellow Ackie Monitors
And Counting...