I have seen it. There is a 20% chance for the scenario in unmodded game, I think; and according to this
mod they are specific to certain lots. I tried in Appaloosa Plains, on the lot Sunflower Shack at 1936 Beach Boulevard. There is a jolly notification like in the other scenarios, about squatters leaving trash behind - and my sim could shoo rats as well as appearantly get them underneath their clothes, unseen by me though; throw away trash and collect the various fresh harvestables laying around; the sort depending on the installed content one have I assume, since I got a banana, pumpkin, carrots, herbs as well as base game ones.