How did he leave work? Did he usually drive or take public transportation? Seems unlikely he would deliberately leave his dog at home alone. But he must have arrived home from work if his personal effects were there.
Leaving all of his personal effects, wallet, keys in the house says to me that either he didn’t leave of his own volition or just stepped outside and was not planning on going anywhere. Leaving a well-loved dog inside and unattended only adds to that impression. Speaking of impressions he strikes me as gay. Good way to get robbed or killed, hooking up online, regardless of straight or gay but they do it with alarming frequency. Hooked up with a psycho or great cover for taking out a problematic individual who wouldn’t keep his mouth shut? Just speculation.