I had a weanling escape the other day when I was trying to sex it to know which grow up tank to put it in. I have seen it, put out humane traps, but so far have not caught it.

Back on topic - I agree with those that say that mouse is probably a bit older than a hopper. Your BP probably could eat it, unless she is a very new hatchling and/or very small. However, if she is refusing it, she might feel more secure with a smaller meal. Or it might be something like she is in shed, or any number of other reasons why she refused it.