Are we able to verify there is only 19.55M mined BTC in existence currently.

so i know the blocks get mined until the last bitcoin is released and thats it, but my question is can we verify there is only 19.55M currently in circulation of whats mined so far?

The US alone is a massive financial market and just about everyone has hear of bitcoin, alot of people own it but how can we verify there isn't more in the system synthetically sold on exchanges? For example people all over the world are constantly buying and selling, retail and institutional investors. I would think given how scarce the asset is and how much interest there is in BTC worldwide the price would be ALOT higher than it is right now.

When you buy BTC on a exchange anywhere in the world, how certain are you, you can actually withdraw to cold storage if everyone decided to at the same time? Is there alot of BTC synthetically out there same way there is more silver in "shares" than actual silver or gold.