A quick update on my Jack Thayer musings. Just to further investigate, I did some poking around online last night -- Philadelphia maps and aerial photos, trolley-car web sites, etc. (I'm originally from the Philadelphia suburbs, and old enough to remember abundant trolleys -- they're extinct now -- so I have some familiarity there.)
I led you slightly astray before on two points: (1) If the coroner's estimate as quoted in the Obituary was exact (doubtful) Jack's demise would actually have occurred at 4:50 PM on Wednesday, September 20, 1945, not 4:00; (2) the location where the car was found, while certainly not remote or isolated, is a *bit* off the beaten track -- Jack was parked on the south side of the road (Parkside) that borders Fairmount Park, a very large reserved recreational tract. (But note: the car was parked on the "business" side of the road -- Fairmount Park is to the north.)
Sunset on September 20 was at 6:02 PM EST. (I checked this with some software I have.) But if Daylight Savings Time was in effect on that date in 1945, it would not have occurred until 7:02 (EDT), leaving almost three full hours (including twilight) before darkness for someone to notice something the very first day. Add to this the fact that the locale and adjacent PTC trolley loop, while not exactly a bustling urban center, was a fairly trafficked area -- PTC passengers and officials constantly coming and going as well as kids playing in the area -- and you have to wonder. (I do, anyway.)
Obviously, the 40 hours is just an educated guess on the part of the coroner, and could have been misquoted by the Philadelphia Inquirer. But it's still an odd affair overall. It's just a gut-level hunch on my part, but certain really things don't gel there, including the purported rationale of Jack's "nervous breakdown" due to "worrying about the death of his son". (Edward had been killed in action almost two years prior; and Marion, Jack's mother died six months after that, on the anniversary of Titanic's collision.)
I point no fingers, and this really is all speculation, but Jack certainly had friends and associates in high places. Whether for the benefit of the grieving family or otherwise, I don't imagine that squelching a thorough investigation would have been difficult for some of them to achieve.