SPINO1:
If we are talking real... i played on Monday and found 3 half decent balls (and i found my own ball)...don't see any laying around here.
That means someone else lost them and didn't find them. If the ones you found were not the exact same brand and model that you were playing you would not have been allowed to use them under the "one ball" rule that is enforced on this game. So, finding a ball in the rough here would more than likely result in you finding a ball you can't use.
For realism's sake I imagine they could program occasionally finding a random ball from time to time. If it's not the same one you are using you could have it available for future use.