Upload & Sell: Off
I don't yet know how good Lr 5.2 is but the problems exporting smaller files has supposedly been fixed. Luckily I was hardly affected by that issue.
It seems that you are letting Lr name its own folders based on the capture date or import date. I don't work that way myself. I import everything into a single folder, applying a file rename preset as they are imported. Then I cull the obviously cullable and move the rest to a folder called "unsorted". From there I will eventually apply ratings and so on and move the files to folders based on the rating (not that this is necessary if I only use Lr, but I want to be able to use other programs to find those files too, without the benefit of Lr metadata and attributes).
If your folder vanished, or seemed to, are you sure that it has the correct date ? Could the date in the camera have been reset so what you know is the latest batch of images from the camera is in a folder with an unexpected name ? That's one good reason for not letting Lr apply date-based names automatically.