It stings a bit...you and your spouse get up the courage to finally take some tentative steps into doing things you fantasized about for years. You post a tame but honest personals ad. You get a response from a nearby couple that seems very, very similar to you....you trade pics, do some chatting, you have a lot in common, you start being friends with them, everything seems to be going well, you start making plans to maybe meet face to face, a low pressure meeting with no expectations...and then they suddenly stop responding to your messages. No explanation, no nothing.
Haven't had a feeling like this since dating in high school. Not sad, exactly...just whistfully disappointed, that something that seemed like it was going to result in at least a nice friendship between couples just disappears for no reason that you can determine.