Crossing the Border without going through immigration (x2) is the easy part. What could be far trickier nowadays is then exiting from Cambodia.
"Back in the day", before Cambodian immigration was computerised, you would turn up at your home country embassy in PP, claim "lost/stolen passport" and get an replacement or emergency travel doc.
You would then visit Cambodian Immigration, pay the fee for an exit permit (memory suggests you are given 7 days to leave the kingdom?) etc. and then fly out.
BUT
Cambodian immigration now appears to be fully computerised, so now immigration likely checks your entry/visa status when you apply for the exit permit, in which case the above will no longer work. It depends on how their database can be searched - if only by passport number then it should still work (because you do not have that number), but if they can also search on name, D.O.B., nationality, etc. then it would throw up no record of entry and so some squeeze would be needed.