Women leave "markers" at a guy's place for one of two reasons:

1) They have an excuse to return later

2) They are leaving "their scent" to warn off other females (just like a dog hikes its leg to leave behind its scent)

Now, women don't want you to know that they do this, and few would ever admit to it. They don't want to confess to this little game that they're up to-- it would be embarrassing if men found out.

And because we men never do this, we're largely oblivious to their employing this piece of leverage. Have you ever liked a girl a whole lot, and in the morning intentionally left your watch behind because this would ensure your meeting up with her again? Of course not!

Another thing women like to do is borrow t-shirts from men after a night together at the man's place. It's not as if they arrived at your place without a shirt on, so why would they need to borrow yours? One of two reasons: she doesn't want to be seen in the early morning hours getting in and out of her car and home with what's obviously last night's slinky outfit (women are very paranoid about appearing promiscuous), or she wants something of yours that she later has an excuse to see you over. T-shirts easily fit the bill.

So, when you discover hoop earrings on your dresser or her watch on your bathroom counter, be aware of what could be happening. It could be a simple forgetful act, and understandably so given the nature of the encounter.

It's also a potentially great clue-- that she likes you-- but is showing you that she is also willing to employ tricks to win your favor.