Some MetaMask clarification needed, please...

Hey, as you'll probably see below, I'm pretty dumb when it comes to on-chain activity and wallets so please have some patience with me...

So I recently got a new PC and I've just added MetaMask to that new machine.

On the old PC, I opened additional accounts besides the original ones to mess around with some BSC shitcoins, but now I can not find that account on top of the MetaMask. When I click on top to switch between accounts, it only shows the "Account 1" and the options to add others (add new, recover with private key or add a hardware wallet).

Does that mean if I don't have the private key to those other accounts, they're lost?

I don't remember what coins they were, probably dead, but I want to use this as a learning opportunity since I still keep most of my stuff on exchanges, and if it turns out I blew the accounts, there's a good reason to keep it that way...

Thanks in advance!

(admins, I'm not even sure what flair to use, my apologies..)