Assuming you never got the prize, better luck next time.
I’m just guessing, but we have a huge retired military population, being just a couple of miles from Eglin AFB main gate, and Pensacola NAS 40 miles west and Hurlburt field right here.
I’m just gonna guess that the ‘owner’ of the rifle died, and had hidden his weapon in the baby box, for whatever reason. The box was sealed with clear shipping tape, and no one bothered to look inside, believing the contents were what was shown on the box, a baby bouncer.
The relatives came to dispose of the possessions and just donated them all to Goodwill, not bothering to look inside the box....................