On my previous post, I has suggested that principal couldn't reallocate funds. After I posted, I realized that may not be the case and I wouldn't want to lead you down the wrong path! So, I'd recommend a sit down with your group and the principal, hear each other out, and go from there.
It sounds like there is more to this story...Something likely led up to this action. The PTO board needs to go see the principal, and sit down and discuss what is going on. Also, are there two names on the PTO bank account? Often the PTO president's name is on the account. Certainly, if the funds were raised for specific purposes, it is not okay for the principal to "take'' that money and use it as he or she sees fit.
I have recently found out that all of the money from our last school year that was collected by the pto was taken over by the schools principal. the pto president locked the pto treasurer out of the bank acct. so she had no access. all of the middle schools money collected is also gone ( collected from dances and dress down days) this is a charter school school that is heavily in debt. how do we make our principal accountable?