Sometimes when it's out/or you just kept it- double clicking your pet makes you disconnect. It happened all the time to me in GS2, a few times at himes, and in HTPQ. Not sure if this only applies to the brown cat or all pets in general. Cheerio!
Applies to un-equipping all pets if they have been out longer than 10 seconds. Bug has been around since forever. But I guess people notice it more now that pets stay out all the time.