For reference only:
LastPass: Free Password Manager 4.1.80.2beta installed, disappeared, worked around by a quit from Firefox 56.x.
LastPass Premium support ticket:
- 6308242
From the foot of my report to LastPass:
… doubt that we’ll make this issue reproducible.
It reminds me of LastPass ticket 6101942, where Xmarks Bookmarks Sync was inexplicably absent and nonfunctional whilst installed.
From my most recent comment in the ticket:
… With an assumption that the bug will not recur, I’m happy for this ticket to be closed. With the user community and developers in mind: if you receive comparable reports from other users, please feel free to reopen here, or ping me in the topic at Mozilla Discourse. …
(6101942 was partially discussed under Xmarks Bookmarks Sync (previously known as Xmarks Sync) allowing multiprocess (e10s) and using WebExtensions APIs - Add-ons / Add-on Support - Mozilla Discourse.)