In 1990 I submitted one of my first (and very few!) 2-movers to the 4th Bron Memorial in Ukraine: a 6-piece miniature realizing what I believe is called the "French-Soviet" theme (most probably the "Letztform"). I have never received a response or the tourney award, and over the years I tried many times to find out what happened with my problem, without luck. I could not find it in any database, and all my contacts had been unable to shed any light. At one point I considered publishing the problem elsewhere, as I thought, with my very limited expertise in the 2-movers field (I only composed and published a total of 8 mate in two problems, 5 being awarded), that it is a neat miniature, but I did not want to make a common mistake and end up with the problem being published twice (my gut had been still telling me all along that the problem was both received and considered for the tourney).
A few hours ago I checked (not for the first time!) the online "Yet another chess problem database" and, to my surprise, I've found my lost problem! It was added to YACPDB on July 24, 2009, from Klaus-Peter Zuncke Miniatures Database: http://dt.dewia.com/yacpdb/?id=151035. Of course, also finding out that the problem had received the 2nd-4th Prize was a sweet consolation! However, 19 years have passed since I sent the problem to the tourney director, and 18 and a half years have passed since the award was published (Westnik problemista, February 13th, 1991)! This might not be a record in itself, but at the same time I think that is not something unheard of, in contrary, it may very well happen more often than we think or it should, thus my open question to you is what was in your case the longest gap between the moment you sent a problem to a formal or informal tournament and the moment you actually found out that the problem was published and (eventually) awarded?!