If your answer was given in the bounty period and it has earned 2 upvotes but it was not accepted, then after the bounty period has ended + 24 hours, you will receive half of the bounty.
This automatic mechanism is useful for where there is a good answer as recognised by the community but the bounty offerer has not themselves manually offered the bounty:
Let's say the bounty offerer did not come back in the 7 days - the community mechanism takes care of this issue.
Let's say the bounty offerer did not think the answer given was the answer they were looking for - again this community mechanism recognizes the effort put into the answer
The bounty offerer and the original poster does not have to be the same - the bounty offerer has the "control" on this. Thus, if the OP never revisits their question, its up-to the bounty offerer to either manually give you the bounty, or yourself to give a great answer that persuades everyone else to upvote you.
If you did not receive more than 2 upvotes, then the bounty will not be awarded.
More info about the bounty system can be found:
How does the bounty system work?How does the bounty system work?
