B737-300 Captain reports Maintenance falsely reported a log book discrepancy as having been repaired. After refusing the false Maintenance Release; a Technician defers the item.

Narrative

Purser notified me that an armrest was broken and drooping down. I wrote up the discrepancy at 25 minutes prior to departure; and informed maintenance of the write-up. 7 minutes later; I received a new release stating that the armrest had been replaced and the release verify function showed this to be a current and valid release. When the Agent came to close the door; the Purser advised me that no Mechanic had been on board. I walked back to the seat in question and found that nothing had been done to the armrest -- the Mechanic had simply signed if off as fixed and did not even come up to look at the seat. I called the Maintenance Control on the landline and informed them of what had occurred and a report would be filed. A Mechanic finally showed up and decided to defer the armrest then sent us another release. With the work actually done right; we departed. Signing off work that has not been accomplished can be a dangerous practice; particularly if you say it's been fixed. On-time performance is one thing; but I thought safety trumped all. It did not in this case. I have all the relevant documents (first write-up; bogus release stating replaced armrest; and final deferring the write-up); and will turn them over if needed to investigate.