Broke a mission that cant be completed, what now?

Hello again.

I was playing a mission in Act 2 “Grassy KNoll” where I was supposed to dock with some “Sniper Cannon Ammo” disguised as a “Books” crate. a Few things seemed to gow wrong. First, I actually somehow got sniper cannon ammo from a different cache. Second, I accidentally told Jaff t pick up teh sniper ammo in the “books” crate, which he did. In the end, I can no longer complete “dock with sniper ammo.” I think I may have killed the target at the “meeting” in th e station with my sniper cannon, though (though I had no image zoom). BUt nonetheless, this mission remains on my Onbjectives list with teh docking part remaining incompete.

There is no way to complete it now. Will this prevent me from graduating to act 3? Is there a cheat to “autocomplete” a mission?

Thanks.