Loss of legitimate emails in evolution 3.12.11 / F21

[Donald Buchan]

Yesterday and today I'd had the a curious experience with Evolution
3.12.11 on my F21 machine.

Friday and Saturday I was cleaning through my email inbox, triaging
various accumulated emails to the trash and various subfolders, such as
"such&such's wedding", "emails regarding the cottage", etc.  I began
suspecting that the occasional email was just "disappearing" when I made
transfers to other folders, as in of four consecutive emails I would
select three, with one in between unselected, make the transfer, and
find that the unselected email would have disappeared.  Initially I just
lazily allowed for the possibility that somehow it had gotten
transferred to the subfolder, and I wasn't too interested in confirming
either way.

Saturday evening I received a legitimate (though mass-mailed) email from
an online retailer with information regarding a purchase I'd made.

I opened the email, and incidentally had to manually load the inline
picture that was attached due to the settings I have.  No trouble.

Then I closed the email by clicking on the little "x" in the upper-right
hand corner of the window, fully assuming that the email would stay in
my inbox (this of course is normal, expected behaviour; that I mention
it of course should raise flags.)  Upon looking in the inbox, the email
was nowhere to be seen.

I checked the junk box in the possible expectation that for once the
spamassassin plugin had actually worked -- which it never seems to given
all the spam that does get past my ISP, and the perpetual absence of any
messages in the junkbox -- and the email in question wasn't there (and
yes the folder was empty).  Then I checked the trash box.  The email in
question wasn't there.

I even did a filter search for a part of the email address in the inbox
as well as in a few other folders.  No luck.

No, I had not deleted the message.  However, personal custom forced me
to concede the possibility that I may have done "something" without
realizing it, and I moved on.

This morning I emailed the merchant to resend the message and surprise
surprise they resent it to me quickly, on a Sunday morning.

I checked the message which this time had a pdf attachment of the
message; I opened the pdf, consulted it, and didn't bother to save it
despite inklings that I should before I closed the viewer.

I may have closed the email in question, and in any case I checked my
inbox and the email was gone; it wasn't in the junkbox nor trashbox.  I
repeated the above experiences, and am now convinced that somehow
something has happened that in days gone by would have be attributed to
proverbial gremlins.

I find this curious since beyond suspecting that yesterday I may have
lost a few other emails, this happened twice to two emails from the same
sender.

Putting aside repeating my request to the merchant in order to receive
the email yet again, possibly doing any of the following, has anyone had
this experience, and if so, figured out how to prevent it from happening
again, and possibly how to retrieve the emails?

- use another account such as my work email
- use another computer such as my laptop or my work laptop
- use my webmail instead of evolution
- save the attachment the moment the email arrives
- take a screenshot of the new email and save that
- etc. etc. etc.

Thank you