Column type changed "spontanously"?

I have several columns that were created as "timestamp without time zone", but I changed them in 2014 to "timestamp with time zone". Recently, when I got notified that times had suddenly changed, I checked and found the columns had reverted to "timestamp without time zone." This seems impossible, yet it seems to have happened. Any ideas on what could cause this? My application has the privileges to do this, as it changed the data type to support time zones. But there is no code that could change it back not to support time zones.