Sorry in advance, this sounds really funny when you forget to buy where the site, exchanger or wallet is. just try searching your laptop's histroy. how to click in the upper right corner of your browser, then search for crypto-related history. then match the password or private key that you have.
It's possible that OP used a browser that doesn't save his browsing history and sometimes you could forget things when you're very busy.
I agree, browser history is the main door to help the OP to recall its activities at that time and there will be seen what has been visited, because without it all we also can't help OP, if OP don't remember anything about its ETH purchase, is it on exchange or a wallet? If on exchanges, there is an email connected at the time of registration, but if it is in a wallet or third-party app then usually there is a backup that has been downloaded to restore it.