If the person that took out the loan cancels it by some kind of fuckery, then you could likely call it stealing.
If it's the entity that made the loan, obviously not.
If it's an agent of the government, which is ultimately the expression of the collective people which defines what stealing is and isn't, then it would depend on how it was achieved. If the agent of the government acted within the law as established at the time the loan was cancelled, then it can't be stealing from a legal standpoint.
Now, is it ethical? That's a different question. It could be seen as a form of theft, but I would argue that it is no more or less theft than taxes, fees for government services, interest, etc. If it is stealing, then pretty much every government enforced payments are theft to begin with, which includes the interest on those loans.