I don't know about people worrying about transmitting the virus through the mail, but other factors do have to be considered when thinking about trading. Some people might understandably consider card trading to be relatively insignicant in light of everything that's going on, and not want to go out to public places. I personally just mailed three trades at the post office on Tuesday, and it was kind of eerie. Not nearly as busy as usual, and the people in line were "social distancing" themselves a few feet apart. I've also noticed that mail delivery is slower. A simple PWE mailed to me from NC on March 7 didn't arrive arrive until yesterday.
The bottom line, as already mentioned, is communication. Not that you have to justify yourself and why you withdrew the offer, but the other person might appreciate a message.
Canadian member collecting John Olerud, Toronto Blue Jays team sets, and Topps base sets.
Always open to trading! Cardboard Corner