Originally Posted by
SDF_Traveler
FWIW, even if you go by your passport, there are some countries that do not stamp your passport on a regular basis in my experience.
I've made many trips where I have departed the US, transferred planes in AMS, arrived in a 3rd country where my passport was not stamped on arrival - nor was it stamped on departure. I then fly back via AMS, then to the US where they don't stamp my passport at the point of entry.
The only record I have of the trip upon return is my credit card bill and bank statement of ATM withdrawals

Still, US DHS has issues with figuring out where I came from even on commercial flights where the entire PNR has been fed to them, including several times over. Here's one exchange: "Which flight did you just come off from?" "The same flight as everyone else here, ___ ___." "Well, that's strange we have no record of you in here." [CBP agent hits a bunch of keys, down, down, down, down the screen.] "Ok, welcome back."