Just one of the situations that landlords/agents must deal with. Never mind a date that stands you up, this one can hurt in the pocketbook.
You can look at this predicament this way.........if the person was not sincere enough to meet with you for a viewing of the rental space, do you really want that person as a tenant?
If the prospective tenant has communicated with you to let you know something has come up to prevent him/her from honouring the commitment.......that's the person who will notify you if something goes wrong with the rental equipment, plumbing, electrical, etc. And you do want to keep informed as to the condition of your rental. This is also the person who will give you a heads up if one of the post dated cheques he/she has given you needs to be held for a couple of extra days.
I certainly love people who "communicate". It avoids creating scenerios in your own mind.