This is really rather odd! I can't say in my several years using Evernote that I've encountered this/these particular issue(s) so I can't offer much more help than what is already posted in this and other threads about losing and recovering data, though others on this board have experienced this, they may have specific suggestions, Also I wonder if this might be two separate issues...?.Either way I strongly encourage you to submit a support ticket if you haven't already. Data loss is very bad. I did file a support ticket. the solution was to remove the evernote local database on the mac and have it re-sync from the cloud. This is a pretty common fix which i've been recommended to do a couple of times already in the last year or so.
I've started to see it recently too. Couple of different scenarios: 1. Shared a note publically. It was still accesible at the public URL, but no longer found in evernote on my mac. So fortunately, i could copy the public content back to my notebook and recover the data. 2. Created a note in my synchronized notebook, put that note in my shortcuts tab. a few days later, clicking on the note doesn't bring up the note in evernote on the mac, and the containing notebook doesn't show it. The note shows on iphone evernote fortunately, so i can email myself the content.