Today, I spotted two LMB 10-12 inches hanging out with some BG I was feeding. I never stocked any LMB that I know of. How big would they be if they were 2 to 3 inches and in my initial stocking of FHM in September of 2015? Otherwise some idiot bucket stocked them.

Fingerling bass with the FHM in Sept 2015 would be around 12" in Feb 2017.

I would think LMB fingerlings would stick out like a sore thumb in a bag of FHM.

Going to try to catch them out, or just leave them?

I may try to catch them out and eat them. I will first try to see if there are more or just those two. I doubt a single pair could spawn successfully with all the larger BG and CC in there. I had pretty much decided not to stock bass and let my 14 albino CC get big and be the top predators. (At least three of them already exceed five pounds). I fed the BG a couple pounds of Optimal Jr today, and there are hordes of 3 and 4 inch ones, probably from the first two spawns last year. In the initial stocking on September 26, 2015 the FHM were so crowded in the bag (500) I got that I didn't look at them too closely. Could have been a very few LMB the same size and they would have gone unnoticed.

I am thinking that they got in with FHM. Bucket stocking less likely.

We electrofished two central Texas ponds last weekend. One is 2.2 acres, the other is 4.8 acres. Both were built seven years ago. Neither were stocked. The owner wanted to stock both of them, but on a preliminary site visit, I noticed some small bass hanging out in shoreline weeds. I suggested we electrofish before stocking any fish. There's an upstream lake, across the highway.
It's a good thing we did.
Both of those lakes had mature populations of bass and bluegills, with a few adult bullheads. I've never seen such a good ending, in this case. During timely floods, just the right numbers of bass and bluegill migrated and established.
For this landowner, it meant he didn't have to spend money to reach his goals.
In your case, unwanted bass could be a problem. You better get them out before they spawn.
How'd they get in there? Reputable hatcheries can make a mistake, especially if you are buying fish off a truck. It's not hard to mix species. But, conscientious suppliers go to great lengths to keep from mixing species.

I bought them off a fish truck run by Farm Cat of Lonoke. Website is stockmypond.com. I am so far from any fish farms that it's risky to go get them, so I need to rely on the fish trucks. In the last batch of FHM I got last spring for my forage pond, there was a hybrid BG in there about 4" long. I got it out before stocking.

There are no fish bearing waters above my pond. It has very limited watershed.

Update: Still haven't caught the LMB. I think there is only one. The other strange fish that I thought might be a LMB came up for pellets and looks almost like a White Bass or HSB about 12" long.

Beware of big bags of "FHM".