problem with the client

[brigo92]

i, i'm Paolo and i'm a newbie in this forum.
I have a problem: i have Filezilla client with the connection to our hosting (on this there are 6 websites). Yesterday my employee had installed on his computer Filezilla and insert the credentials to access on this hosting. This morning 4 of the 6 sites are disappeared!!
How i solve it?

The sites on the web works but i can't see this on Filezilla client (and there isn't hide).

Thanks