Looks like a red belly pacu. Yes, odd that it is not labeled. Perhaps they just arrived and they have not gotten around to it.
Years ago I bought a red belly piranha which was labeled 'Silver Spotted Fish'. LOL of course they asked if I worked for the VA fish & game association. This was in a mom & pop shop. Since we are talking about a national chain store I doubt that this is a piranha. But an interesting example of mimicry.