So, the first Dratini that I caught on community day was small but a shiny one. When I checked later this had not been added to my bag (and it being shiny, I can exactly recall that I captured it). Not too big an issue as I later caught a total of 10, 9 of them bigger, so I found that odd but discarded the thought.
Now yesterday I tried in vain to catch an Ariados. It ran, my son witnessed it and made a comment. Checking my bag, I found that it had been added to my collcetion.
Is that a known glitch that escaped me or why would that happen?