The figure of 3.6 million BTC sounds right for me. Even my initial days I was careless with some of my wallets. I believe that I would have lost at least BTC0.10 due to carelessness in backing up the wallets. Back then, it was not a big amount. Bit now the same amount of coins are worth $3,500. I lost most of these coins, when I failed to backup Instawallet addresses. I had the option of contacting Instawallet admin, but I was too lazy to do that in 2013.
^ also saddened with your loss, friend. before Bitcoin make a record ATH of up to $ 20k the first time, many Bitcoin holders did not care and were serious about storing their passwords and private keys as a result many lost their Bitcoin because it was locked in their private wallets. 0.1 BTC right now is really very valuable.