Stolen?

Got a money order today of the $ I had set aside in the envelope marked groceries.  Since we had been using the tax refund $ for groceries, I should have had $900.00 total in the envelope.  I only had $540.00, so $360.00 is missing.  I remember 1 day, the box I had it in was askew in the drawer, but I thought maybe I had left it like that.
I checked my deposits from the gas & grocery fund, and it still doesn't add up.  I should have had $900.
I guess I need to find a new spot for it.  I hope I'm not missing $ from any other envelopes.