several things here, once you click edit, the draft should disappear because it is not a new draft. I know it sounds odd, but each auto saved version of a draft is a new draft, not a save of an old one. It is just how IMAP handles drafts. Having mail disappear locally is fairly common in IMAP accounts if there are issues with connecting to the server. This can by a up again gone again internet connection, and antivirus product that is having issues or any of a myriad of issues. The first thing to do is try web mail and se if the mail is still there. Because in moving your mail from the inbox, you are basically deleting the email in the inbox and creating a new instance in the folder you have chosen, you are not actually moving something like licking up a pencil and placing it somewhere else. This delete recreate involves a lot of traffic on the internet for an IMAP mail account and at times the folder can loose some information. Simply right clicking, selecting properties and then the repair button is often successful in regenerating the list you see from the underlying data. Fundamentally issues where mail "appears" to disappear and is still in webmail usually fall to antivirus products scanning in the Thunderbird profile folder or other destabilizing things like attempts to place the profile data in the cloud using syncronised location like Google drive. In the first instance I recommend an exemption in the antivirus product to scanning in the Thunderbird profile folder.