It happened me almost three times. You rob a player, obviously you get the wanted, then the cop issues you a ticket and after you pay it, this is what happens:
A message showing "You have been arrested by <cop that you paid the ticket>" then "The <money robbed to the victim> has been returned to <victim>".
So, I don't know why it says i've been arrested and returns robbed money to the victim as when a ticket has been paid obviously you become innocent.
Here is a screenshot:
As you can see, I paid the ticket and it says i've been arrested (which is not true), meanwhile robbed money are gone back in the victim's wallet.