Bryce, you can sometimes retrieve missing data by following the steps in this article. Hope it helps. https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Also, if the first article doesn't help then sometimes missing passwords can be retrieved using the logins-backup.json file within the Profile folder on the hard drive. Although this particular recovery method would need to be attempted as soon as possible, as the backup might later get overwritten.

If you do not know where your Profile folder is, see here: https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

To attempt password recovery:

1. open your Profile folder on the hard drive
2. fully exit Firefox if it is running
3. move logins.json to a backup folder
4. copy logins-backup.json to a backup folder
5. in the profile folder, rename logins-backup.json to logins.json
6. restart Firefox

If this doesn't work then you can always exit Firefox and then restore the original two files.

If you are still missing either bookmarks or passwords after the above, then here's something else to try: https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Are the logins the only data you lost or is other data like bookmarks gone as well? Are You using Sync?

Did you try to reboot the computer?