i have two muppet moments.

Around 15 years ago was heading to Thailand on Thai from LHR with my future wife. No status so planned minimum time at airport. Arrived with about 65 minutes to departure and checked in at the business class counter. Flights delayed I was told due ATC, probably about an hour. Proceeded to produce tickets and find I have neither passport. They are in a drawer 25 miles away!
Cue insults from future wife and cursing from me followed by dash to find a taxi. Very kind and frankly brave private hire picked me up outside T3 and raced down the M4. I got back to T3 where TG had been rather wonderful by checking in bags and producing boarding passes before flight closure. They handed over the BPs when I got back, sweaty, flustered and £100 lighter.

The last time was 18 months ago when I left a leather Concorde document holder in my hotel safe in Saigon. I realised only at the airport and had passed security. There was around £500 in various currencies plus spare credit cards.
There are no phones and mine would work but a Vietnam airlines lounge Angel came to rescue. She called the hotel - who located the wallet, put it and a staff member in a taxi, and sent it to the airport. The lounge Angel got me landslide and I paid the staff member for the taxi with a huge tip.
I was indebted to the staff member who would not take anything for her help. It was a remarkable experience as everyone, at every stage, was helpful and above all totally honest. Restores your faith in human nature.