On my differen devices I sometimes have different magnitude limits due to screen quality or times when I am exploring the database. It seems that, just recently, this caused an object to be missing from my phone's SkySafari database which has a lower magnitude limit than my tablet. On the tablet, I decided on the object as a proxy for a nearby object which is not in your database and immediately created a retro observation on it when I saw the object. The object is PGC 3550012 and has a very dim magnitude of 18.81, which I could see on my tablet while zooming because its deep sky settings for SkySafari 7 Pro have a limit of 17.0 magnitude.
The observation showed up briefly on my phone in both SkySafari 6 Pro and 7 Pro. However, after a minute or so the observation became orange and gave errors that it is not in the database on both of these phone instances. They have Deep Sky limits of 13.9 and 13.8 respectively. When I try to just search on the objects itself in these instances, it cannot be found anymore even if I increase the mag limits. It has been about 5 days and the object can still be found on my tablet and the observation is still found as well. I think this may be what also happened with object GAIA 2090688104292041600, which is a synonym of Beta Lyra D and has a magnitude of 15.20. This observation was recorded last October and the object cannot be found on any of my devices at this point (I'm sure I have modified mag limits several times since then.)