When to stop payment on a check

I write a check for my rent, one for my car payment and (sadly) one for support to the ex-wife (which I could do by electronic transfer but I like to make her have to go cash a check).

Everything else -- utils, cell, cable, credit cards, etc. -- is done online

 

You can leave as little as $20 on it and have it set up to automatically withdraw from your checking account or credit card. Really, it's not a big deal.

 

I currently have $3.17 in my checking account and I have no savings. And $4 in cash. So yes, it is that big of a deal.

 

As of today, I checked my checking account and apparently, the bank that has my car loan still hasn't received the check.
When I called that bank last week, they said they'd send me the paperwork to set up the automatic transfer. Curiously, I have yet to receive that paperwork.
That should help me in the future, but is it safe to assume at this point that the check I mailed two weeks ago will never make it where it was supposed to go?