JenB - I don't mean to scare you, but if you saw one there's probably a dozen somewhere close by.
They absolutely LOVE tomatoes.
How do I know this? A couple of months ago, we had a rat invasion at our house from a hole that was created in our kitchen remodel (behind our new fridge which was in a different spot than our old one). We have lived here for almost a decade, and prior to this incident had NEVER seen any type of rat or mouse inside the house (which is actually pretty common in southern FL).
What was my first sign? A big bite out of a tomato on one of my counters (!!!). We started seeing lots of other signs (droppings) and my son actually walked out of his room and saw one. A baby rat got into his room. It was so, so disgusting.
Let's just say this traumatized me beyond belief. It took me several months to get over it.
I had three different pest control places here in one day, and basically threatened my husband that we would move out if we didn't get it taken care of THAT DAY. One of guys told me about the tomato issue. It took several days to figure out where they were coming from. We actually had to camp out on our boat.
Yes, yes, yes - hire a company. They will know what to do outside. They can place bait boxes that only the rats can get into. The bait kills them, usually about the time they get back to their litter. You can also buy these boxes, and the bait, at Home Depot.
If you don't eradicate them they will start gnawing on places to get in out from the weather, etc. You DON'T want them in your house. We have tree rats in southern FL and they love to gnaw in through vents to get into attics.
Good luck - don't ignore this issue.