I read some old threads about lost Bitcoins ND this question has been on my mind ever since
If the lost Bitcoins were for instance recovered will the price of Bitcoin drop because in theory it would affect the amount of Bitcoin in circulation which will lower it's price . I saw in those threads that lost Bitcoins are considered a donation to the Bitcoin network. so if my theory is correct then we should be happy those Bitcoins were lost.
Lost bitcoins are not a voluntary donations to the network. They are involuntary. Irresponsible storage or the neglected necessity to take care of how you store your Bitcoins is one of the reasons that they will never be able to be recovered. I doubt many of those who lost their coins voluntarily destroyed their access to them.
There will never be a case where all lost Bitcoins suddenly become available to their owners, so there is no need to theorize how much the price would drop if that were to happen. Though yes, the price would drop as instantly a lot of Bitcoin would enter supply rapidly.
Should we be happy? Not really. It's better that Bitcoins are circulating and continued to circulate since that period of time. It creates more ecosystem activity, it creates more use-case and it makes the network more active. Is it economically beneficial right now that these coins are unlikely to ever be circulated again? Sure.