I'd send it back, but not so much because of the partially uncovered trigger. Drawing won't put any forward pressure on the trigger, and while holstering it's always your job to keep the trigger protected until the gun is in the holster. Once the gun is fully in the holster, the trigger is fully covered by either the holster or the waistband on your pants - nothing can get to it.
No, the reason I'd send the holster back is so I could replace it with one that has its belt attachments somewhere other than right on top of the cylinder, the place that's already the thickest part of the package. AND that allows you to tuck your shirt over the gun and between the holster and your pants. You probably won't need to do that very often, but it's worth having the option the few times that you do.
The Lobo IWBs have the offset belt attachments, but neither the "belt loop" models nor the offset clip type appear to be tuckable. It looks like almost all of the Charter Oak models for revolvers have their clips on top of the cylinder, so I'd skip those. None of the Don Hume models appear to be tuckable. The Simply Rugged model for J frames looks like an OWB model that can have straps attached to make it an IWB, but it doesn't seem to be tuckable.
Of tuckable models I'm aware of, DeSantis has the Intruder with two offset clips, while their FlexTuk has a single clip. Crossbreed has 2 models that take a J frame, with one or two belt clips. Kholster offers a very similar design that's a lot less expensive than the Crossbreed, but benefits from some trimming with a utility or Xacto knife once you have it set up the way you want it, to let you get a firm grasp on the grip for the draw. (I use a Kholster for my 649.) Side Guard also has several offset clip models that are tuckable, some with one and some with two clips. I like their Tuck Clip model, which is what I use when I carry a 442 (it's a good bit lighter than the 649, and is reasonably stable with only a single belt clip.) CompTac makes their superb CTAC for J frames, but I find kydex to be uncomfortable against my bare skin in the summer.