What have you tried to retrieve them?
My case is a bit more complex. Normally I take backups of my Bitcoin wallets, so there is no question of losing the access. However, I had accounts in a few cryptocurrency exchanges, which are now defunct. Wex.nz and Cryptopia are some of the exchanges in which I had account. When these exchanges closed down, I lost the access to my coins. And worse still, the amount was quite significant for me, at least in the case of Cryptopia.
Wouldn't they post a notice ahead of the closure that will happen or did they just seemingly ran away with all your coins and asset or at least contact all their users through email? It seems like finding a lot of exchange isn't really that good, when you're planning to have a strategy of finding better rate for the coins you want to trade. I never knew these exchanges as I was just sticking to Binance.