Actually, it is. Especially in a strange bed, with more pillows that you would normally have. It probably got pushed against the headboard at night, and simply fell over him.
No one is saying the damn thing was in his mouth.
The story keeps getting changed.....
When someone keeps changing their story... That’s usually a pretty good indication they are not telling you the truth.
The Doctor first said he had a heart attack, then when they asked how she was able to quickly determine this. Then she said he died of natural causes.
The Doctor never physically examined the body. She guessed it over the phone without even looking at the body.