My fiance is a thief!

My bike was broken so I asked my fiance to fix it. A man came to him while he was repairing my bike in front of the apartment house we're living at and asked him...

-What are you doing?
- What am I doing??
- Is that your bike?
- No, its not mine.
- Is it Jakob's? Do you know him?
- I don't know anyone called Jakob. This is my girlfriend's bike.
- Really? (then the guy was looking confused and standing by him since he didn't know what to do)

On that moment I opened the maindoor, I could guess that the guy was having a trouble with my fiance. ”he is fixing my bike”, I said. Then he was asking me if I'm sure that it really is my bike. He was telling me that it looks exactly like his friend's bike who is living in same building. I said him that it's mine and I have had it for last 10 years so it can't be your friend's.... you've probably forgotten like what your friend's own looks like.

He said sorry and explained that his friend is having a bike, which reminds my bike really much. Then he walked away. He had probably thought that my fiance was trying to steal his friends bike. I'm lucky that he didn't beat up my boyfriend due to a misunderstanding.