First find the serial number. There is no "plate" to be lost. It is hand engraved in each hull.
https://www.hobie.com/articles/boat-ser ... cation,15/If an older Outback, you can see old version of websites on Wayback Machine.
https://web.archive.org/web/20180709153042/https://www.hobie.com/kayaks/mirage-outback/Outback (does not sound like the Outback as it is longer):
SPECIFICATIONS *
Crew: 1
Length: 12' 1" / 3.68 m
Width: 33" / .84 m
Capacity: 400 lbs / 181 kg
Fitted Hull Weight: 81 lbs / 37 kg *
Fully Rigged Weight: 99 lbs / 45 kg *
Hull Construction: Rotomolded Polyethylene