Definately follow up with the vet.
I drove by frequently and drove up the driveway of my 'friend' with the starving horses. I had told her I would. I said I wanted to see full water troughs, recent farrier work, hay in the barn, and evidence of hay in the paddock. I never talked to her again, I just drove up and looked.
She only had temporary custody of those horses, she was keeping them for someone who was working in Alaska for a year or two and would return. When they returned and took the horses back, who did not look too bad by then, I shared with them what they had been through.
I still drive by there once in awhile, just to make sure she doesn't have horses again.
Around here, driving up in strange people's driveways and poking around will sometimes get you shot. I want to do all I can to make sure this horse is really being taken care of, but I really don't want him to know that it's me that's causing him trouble, now that he knows where my barn is.