In Canada it will come down to whether or not you are a "bond fide purchaser for value without notice."
The facts you present suggest that you were aware prior to purchase that something might be off, a discount of 33% off retail before taxes for a sealed box should raise suspicion. You followed that up with questioning the seller as to where he got the drone and asked for a receipt. He told you it was a gift and he already had one.
You then proceeded to activate the drone and do a test flight, all of which is reasonable. You paid him and then took the drone and went on your way.
The question is at this point have you done your due diligence? It would seem that you have, unlike cars or most other forms of expensive personal property, I doubt a PPSA search would yield much, though you should always do this when buying higher value personal articles (vehicles, travel trailers, etc).
The potential trouble arises from your subsequent messaging sellers and realizing it is the same person. You can safely presume now that something questionable may be going on.
You also posted your doubts to a public forum which can be accessed by anyone. You should not in any circumstances purchase another drone from this individual as it may taint the first purchase.
This is not provided as legal advice and is merely an opinion. Should you require legal advice, talk to a licensed lawyer in your province.
