You know, I find that min raise to be rather strange.
It seems to me that he was in one of those "half-way" moods. It seems if he really wanted to make money he would have just called and let you keep betting.
If he was afraid of the flush possibility he would have raised harder to ensure that suck out didn't occur.
It seems like a combo of both, he wanted to make chips and scare away a potential flush.
However, when I read the title I thought you meant a min bet on the flop, not a min re-raise.
Any re-raise that isn't power is usually to get more chips. An all-in re-raise is usually a semi-bluff...
So if he re-raised and didn't shove, prob means he got a monster.
But the min bet on the flop, I see a lot, anywhere from a draw to a monster. That is really player dependent.