I'm really pissed off because all the emails were really important and I was only able to confirm that they've ever being sent via phone call. Oddly enough but Google has "emails gone missing" support form which I filled out. https://support.google.com/mail/contact/missingemails?rd%3D1
Now what should I use instead? I'm ready to pay for a more reliable email provider. Who would think that Gmail isn't?
P.S. I also found this comment here https://news.ycombinator.com/item?id=12247401
"GMail once ate (bypassed spam and instantly deleted it, silently) an email filled with travel itinerary for an interview, causing me to miss the flight booked for me and the company I was interviewing with to have to book a second one (~$1k). If you find this hard to believe, go check your spam folder and see how many emails you have. Do you think you're really only getting ~1 spam message a day? This is the dark side of Google's spam filtering."