First please read old post: Re: Mu didn't save work done for a few days.
This has been a concern (and a very confusing one) for some time.
In the last 24 hours I managed to observe this happening.
Yesterday I changed the layering order of elements on a page to address a customer's feedback.
I changed the layering order, uploaded it to business catalyst and sent a link to the customer. Other changes were also being undertaken at the time.
I would upload to BC, test on Desktop and Mobile, and then inform the client the changes were ready to view.
The layering order was changed and was correct on the BC test site when viewed by myself and the client.
After doing this I saved my file, closed my laptop and went to launch.
Upon return, I recommenced working on the site and making more changes.
In all, I did about 6 uploads to business catalyst. After that I contacted my client to let them know all other changes have been done.
I saved my file, closed Muse (without it crashing on save or close - which it does 80% of the time) and closed my laptop for the day.
This morning the client contacted me saying the layering order was still wrong.
I assumed the client was viewing a cached file and told them to go through all processes to clear cache and historical data and reset their web browser.
Then I went and checked the testing server:
There few other changes that had 'vanished' also, however I think my point is made.
My procedure is to open the .muse file from within Apple's Finder to prevent opening an incorrect our outdated file.
I do not have duplicate a file on my computer or remote location.
When I backup up a file I do it manually by copying the file, renaming the copy and storing away from the working file.
I followed this process for over a year now to eliminate user error in this scenario, which is quite frequent.
On an Apple Mac OsX computer edits may be lost, in no particular order, when the device goes into sleep Mode when the .muse file remains open, or Muse hangs or crashes upon Save or Close.
Being that I noted another user reporting a similar issue in 2013 and I have been suspicious of this possibility for a long time myself, and now having a logged event of the occurrence witnessed and noted by a third party, I am very suspicious that is in actual fact real, and has remained present in all updates to date.