The OP described the accident he saw and stopped for, so I've been posting with similar MVC severity in mind, I'll make sure to clarify that in the future. I'm not saying I stop for every little thing, but if there is a possibility that injuries have occured, I stop. Similar to appraising the damage to your vehicle before calling the cops for a fender bender. Here, they say not to call for a squad for less than $1000 damage unless there is a disagreement between parties (uninsured driver, etc). If I feel there was enough force behind the colliding vehicles to cause injury, I stop. If there is significant damage related to the method of collision, I stop.
I didn't assume the reason you didn't carry gloves was space, but you said in an earlier post, " Further with no equipment, what skills am I performing?" I was just trying to point out that lack of equipment is not a reason to not stop. If you were one that would stop, but doesn't because you have no equipment in your car, all you need is a pair of gloves to perform some more basic skills.
Also, I don't identify myself as an EMT, I usually say something along the lines of "I'm trained in advanced first aid, may I help (you/your child/whomever)?" If the BLS unit arrives there and wants to know more, I identify myself and my training level to them.
As far as abandonment goes, you're putting this person in the hands of on-duty trained professionals that have the means to treat and transport the patient, and you're following the continuum of care, not just stabilizing c-spine, then walking away when they arrive on-scene. I don't see anyone finding that as abandonment.
I may be misinformed, but I believe that in MN, I am required to stop. Some of the other people I personally know also say that if you are trained in skills that could be useful and can safely do so, you are required to stop or administer aid if the victim gives you permission, and you act within your scope. Driving by would be considered neglect, which is a breach of duty and can lead to liability. I may be wrong, but that was my understanding from the conversations we had in class and some of the conversations I have had with friends that are also in a medical profession. MN is weird about other things, so it would not surprise me.
Again, with state-to-state laws varying so much, this may not apply to the majority of people here. If I am injured (say another vehicle hits me) while getting in or out of my vehicle, or approaching my vehicle, my auto insurance has to cover any medical costs I incur - ER, Chiropractic, Physical Therapy, etc. As for accidental exposure, my health insurance would cover my testing and care, as deemed "medically necessary" by my physician.
So, I give you this for thought: You're driving home from work, and see a vehicle change lanes into another vehicle, causing that second vehicle to hit the gravel on the side of the shoulder, and skid into the ditch. You call 911 and report the accident, but drive on. The following day, you find out from your neighbor that her husband was the one in that accident, and has a broken leg, a couple fractured ribs, and is in critical condition because of the lack of oxygen from respiratory failure, secondary to the chest trauma, during the 20 minutes it took the BLS unit to get there. Knowing you could have assisted his respirations with just a pair of gloves and a face shield, do you think you might have stopped?