(Original Publication Date, 14 June 1991)
Panel 1: We continue on with Maeve noticing that John and Elly are holding hands which leads Cecily to the conclusion that she's taking him back. When Maeve huffs that he doesn't know how lucky he is, Nilda channels Jean by growing MEN!!
Panel 2: Since John has been hearing Elly mutter MEN under her breath since he first forgot to put the toilet seat down, he finally notices the people the next table over and asks Elly if she knows who they are. Elly says that they're people she knows from work and that she thinks that they're talking about her and John.
Panel 3: Since John is really bad at reading body language for the purposes of the joke, he can't decipher the big, phony play-the-innocent smiles Team Gossip have on and asks Elly how she can tell.
Summary: Given that Elly alludes to staying out later than she expected, it is most likely that in the strip in Lynn's head, they were told the truth. Since I'm a fungus troll snarker person because I hate watching John talk shit about his crazy wife to everyone who can't avoid it, it works out better if they die in ignorance because John needs to pay for his years of bitching about how horrible it is to have a life 99.999999% of the people on Earth envy bitterly.