I have not personally experienced this, but there are so many ways our loved ones can communicate with us that seem so absolutely unlikely, that I have no doubt that this is possible.
More than one person on this board has had what they call an "overlay," I think is what they've called it. They will see someone in a restaurant, grocery store, while driving down the road, etc. That person will look VERY much like their loved one who has passed. Then they will pass near that same "look-alike" a few minutes later, and the person doesn't look like anything like their departed loved one at all.
It's as if the passed loved one overlaid their own image onto a person of similar size and shape for a few moments, so as to send them an ADC or "Hello from Heaven"! :)