Your situation may be different since your deposit was at a state school that
possibly does not use the Common Application or have a policy against double depositing. Hopefully your college counselor knows the rules and kept you within them. In that case the only risk is the inconsequential loss of a deposit.
In most cases the actual risk of using a secret Plan B is dealing with anxiety as you pray that Plan B (or your college counselor) does not follow through and report the violation to the service academy, thereby making you the test case for what the academy will actually do in this instance (no one on this forum knows what SA admissions will do).
I know of several instances where Plan B said no problem, best of luck to you. I also know of four cases in which appointed candidates were caught using a Plan B without the Plan B's knowledge and were confronted about the violation. In all cases they were distraught at the possibility that service academy admissions might be contacted. They were polite, humble, and apologized. Fortunately, there was no follow through in these cases and the extent of the "punishment" was a few shattered nerves.
In none of cases did the candidate or family tell the college to take a hike or dare them to follow through, as some on this forum have suggested is the appropriate response. The reason I am so argumentative on this issue is that in one of those cases the idea and advice to deposit at a Plan B came from this forum - without the benefit of my sage advice about possible consequences.