Can somebody here tell me where does the Patriot spams in SP? I may test-upgrade it there to see if I should FM one or not since I have already fetched one in MP.
Look around in Hawick, where Michael gets his IT-Gear for the mission Friend Request. You can also look around in Chumash and the road leading from there to Fort Zancudo.. Small change you can find it in Grapeseed too.
It also helps switching back from online to singleplayer when Patriots start spawning in your multiplayer session, switching back will make Patriots spawn in Story Mode for a small time.