This report published buy the United States Bureau of Alcohol, Tobacco, Firearms, and Explosives contains statistics on the Federal Firearms Licensee Theft and Loss from January 1, 2016 to December 31, 2016. From the report: "Queries of the Firearms Tracing System (FTS) were used to determine which firearms were reported in Federal Firearms Licensee (FFL) Thefts/Losses. This information was extracted from the FTS on February 17, 2017. FFL Theft/Loss Reports where the reported theft dates were from January 1, 2016 to December 31, 2016 were selected. Firearms reported in FFL Theft/Loss Reports and subsequently determined not lost/stolen were excluded from the totals."
Bureau of Alcohol, Tobacco, Firearms, and Explosives: https://www.atf.gov/