Your saved flights are in ..\My Documents\Flight Simulator X Files\...
Did you physically delete files from their folders or did you use the 'delete' function in the sim?
1-If you physically deleted the Trike Ulrtralight from your ..\Airplanes\.. folder,
restore it.
2-If you physically deleted the files from ...Program Files\Microsoft Flight Simulator X\Flights\other\....
restore them (several *.FLT and *.WX files)
Both of these are needed so that the sim can revert back the 'factory' default flight.
See the
Flight Simulator X FAQ's to locate your 'fsx.cfg' file.
Make a backup of the 'fsx.cfg' file and then open 'fsx.cfg' in Notepad.
Find the following section and delete the path entry from the 'Situation=' line. This will cause the sim to revert back to using the 'factory' default flight (Trike at Friday Harbour).