Emails deleted?

Hi there

I am new here.
I am using the EM Client, and using an online webmail.

So today, I was looking at the emails on the online webmail in the browser. When I came home, and opened the email-client, the emails were gone? - I use a pop3 adresse, which to my knowledge downloads the emails and stores them. It is said to leave a copy on the server, and delete after 7 days.

But at least two of emails that I know of are gone.
Where did they go?
I cant find them

please help.