Are you insane?
You want to get your car "lemoned" b/c it went into "limp mode" 1 time?
Relax, Francis...it will be ok. Most "limp mode" occurrences (which are still a small % of 335i's), including mine happened 1 time just like yours (cruising on the hwy. at 65mph while in M6), and so far in several weeks, it has not returned in my car.
Did you stop your car, turn it off, and then restart?
If so, did the little yellow light go off and your car return to normal? That's what happened in my case, and like I said, so far so good...no more "limp mode."
If you had a problem with your dealer's service dept. (and any "rude" person handing your call), you should either call or meet with the Service Mgr. to handle your complaint or simply go to another dealer for service. However, jumping the gun by thinking about the lemon law is just ludicrous.
btw -- you wouldn't be able to lemon your car unless the problem reoccurs more than 1 time (in fact, it would have to return many times) and the dealer determines that they cannot fix the problem.