If I was the Judge sitting in front of you and "a worker [that] is suppose to sho up and finish job", I'd like to SEE proof (not 'hear' it) that you gave him MORE than a couple of opportunities to finish job. If you can't prove that, then it's HE SAID - SHE SAID. From there, as the Judge, I'd have to figure that both of you aren't quite telling the truth, and make a decision from there.
Soooo, if I were you, I'd start a Journal. I'd WRITE down dates and times and notes on what I talked about w/the worker about finish job. PLUS, I'd make a note of how I 'talked' to him (either by phone, in person, at his office, at his home, in front of the house, etc., etc..) PLUS, if I send anything to the worker, I'd make a copy and send it to myself certified mail, return receipt, and NOT open up the envelope (when it comes back to me in the mail.) And you'd send the worker ALL WRITTEN COORESPONDENCE via certified mail, return receipt too. Keep your receipts. PLUS, take pictures of the unfinished job. Make sure you get estimates from "other guy" as to the cost for time and material.
So, plan on the possibility that the worker will sue you in court. And then, as a Judge, what would YOU want to SEE as to having given the worker a CHANCE to finish job. Personally, I'd give him 3 chances over a 3 week period ASSUMING this isn't a job that requires more immediate attention. As long as the 'job' doesn't deteriorate over the 3 weeks, that's what I'd do. YOu can wait longer if the same applies. It's your call.
In short, it wouldn't be prudent (IMO) to pay someone else w/o giving the worker a few 'quick' chances to finish the job. DO realize that if he's waiting for material to be shipped in, that's a reasonable excuse to NOT be doing the job. You have to make a lot of notes and consider how someone else would view the situation. If you want this to go in YOUR favor, then back up what you end up doing with PROOF and pictures and notes and so on.