Has this happened multiple times...or just once? If the latter, I'd really not get yourself worked up over it. From what you say, the dog was not in distress...he most likely had sufficient food and water...and maybe even puppy pads "just in case".
Some dogs are perfectly fine being on their own for a long period. It may not be ideal, but needs must. I had to leave Sally once from 5:30 am until about 10 pm...she was fine.
Please don't describe this as abandoning the dog...that is too strong a term...for one incident.