I was a Cop in Texas for 35 years. I'm very sure there was an original theft report, the one your wife made at the time of loss, actually Burglary of a Motor Vehicle. When the gun was recovered a followup report was done. Both reports and any other paperwork relating to the theft/recovery went into the case folder. Just ask for a copy of the original report and of the followup report.
Even if you don't get the Reports, any investigation into a crime committed with this gun should disclose that the gun was 'out of her custody' during this particular time period.