<human>: Summarize the given text in a few sentences.

My friend is 26 and has been dating her boyfriend for over 3 years. They recently moved in together and seem like a very solid couple. 
They have their occasional fights but I've always thought he is a good match for her. 

He's recently been traveling a lot and I'm not sure how that's affected their dynamic. 

She was cleaning today and found a necklace on their bed. It's not hers and she's never seen it before. 
No one else has a key to their apartment. 
No friends have been in the bedroom. 

She asked him about it and he kind of brushed it off. 

So I'm asking for her, anyone else have had similar experiences? 
Any advice?
<bot>: my friend found a necklace in her bed that she shares with her bf. The necklace doesn't belong to her. He says he doesn't know how it got there.