Oh no!! Your debit card!!! I left mine in the ATM machine in Bangkok last month as well, never got it back, bit of a dumb system where they give you the cash first unlike UK where you get the card back first..

I actually preferred Hanoi to HCMC, I stayed in the old part of Hanoi in a really nice small hotel. I found the city really quaint, the food was great had a great massage, and maybe lucky I never came across any scam. HCMC was far too 'city' for me. Hopefully you'll have a better experience if you ever do go back one day.