One time about 8 or 9 years ago (maybe more) way before kids or car seat addiction. I was standing on my grandmothers balcony on the 5th floor looking down into the parking lot. I saw a man come out of the building with 2 older kids and a baby in a bucket. I watched as he tried to buckle in the bucket and he had no idea how it went or where he should put it. He finally decided that the best way to install it was in the front passenger seat forward facing, and that he should take the seat belt and wrap in around the front of the bucket
. When I saw that he was going to leave it like that, he was getting the other kids into the car with no seat belts, I ran down the stairs and out the building to stop him. I just could not live with myself thinking of that poor baby being ejected and killed if there was even a minor accident
. By the time I got outside he was in his seat and getting ready to back out. i tapped on his window and told him he could not have the baby in that position and buckled that way that the baby was not secured and could die very easily. He did not seem to happy that i had approached him or talked to him that way but he did stop and comply. I told him he needed to install the baby RF in the back in the middle and showed him were the seat belt went (this was before bases were common) I knew from having cared for my nieces. I also told him to have the other kids buckled in.
My grandmother did not want me to say anything to the guy but I could not just let him leave. I have seen other crazy dangerous things before like improperly installed buckets forward facing in back seat. Really old seats. FF babies etc mostly in parked cars (well not the ff babies) and have done nothing and I do regret it. I did print out some info I was going to leave on a car window but it was gone when I went back. I guess in your situation if DH was driving I would have had him get close enough so I could verify what I saw and get a licence plate then I would have called the police.