What is your signal strength where you are? If you have a poor signal and your TP keeps having to look for service, it can use up your battery very quickly. I have one grocery store near me that I get very poor signal quality inside and I have had my battery drop 30% while I'm in the store.
If it continues to happen, You may also want to want to run a program like dotfred's task manager. It will let you see what programs are active and how much memory they are using...just in case something is chewing up a lot more CPU than it's supposed to.
And, if it had been a while since your last soft reset when this happened, it may be that some program didn't fully close and was still using resources.
Otherwise, welcome to life with a Touch Pro