I dont think the FBI wet thru Monicas place looking for dope on Clinton, gifts, memos, or what ever..
To be accurate, yes the did. They took the Blue Dress, tested it, and found a positive match for the President's 'DNA.'
That's when he finally fessed up.
"The FBI turned up no identifying stains on any articles of clothing taken from Lewinsky's Watergate apartment during a January search." - link
(She had hidden the dress elsewhere and later turned it over to prosecutors.)
If you google "Monica Lewinsky" and "FBI", it is clear that she had plenty of interactions with them.