No. You don't get my idea. I meant if you don't enter your email address on that site, they likely don't have your email address in their database. Maybe they have it on database or maybe not before the time you enter and search. It is only assumption and the prevention is protect the privacy of your important email address.
When you search for an email address
Searching for an email address only ever retrieves the address from storage then returns it in the response, the searched address is never explicitly stored anywhere. See the Logging section below for situations in which it may be implicitly stored.
They don't necessarily save your email, but they do keep logs.
Anyway, I have personally used it and had some old emails show up along with specific leaks; I can anecdotally say it's legit. It's a popular and reputable service and I would say it's reasonably safe to trust. Either way, they can't really do much with
just your email anyway, which is all they require, and you can always hide your IP using tor, VPNs, etc..