Border crossing rules have changed at San Ysidro

I'm U.S. citizen I crossed Mexico border a couple weeks ago at San Ysidro, Mexican officer on border asked me something in Mexico.. I don't speak Spanish, I realized he asked something ... going to Mexico and I said "si"  then he asked me something I said I don't know Spanish, he asked in English if I'm Mexican, I asked what he meant, and he said if i'm mexican citizen I said, no I'm U.S citizen...then he said this is the line for Mexican citizens, I asked him how he knows if he don't asks passport to people what citizen they are (just 100 of people crossed during my conversation with him and no one asked them passport), he just stopped me, and "I said if this is discrimination?" (my question I think was absolutely rightfully) then he took me to his boss, and boss said I lied officer that I'm Mexico citizen, I said I don't know Spanish how I lied him, I answered in English all... then he asked for how long I'm going to visit Mexico I said one day or less, he said you said one day (just try to catch from me something)!! He asked if I have hotel reservation, I said I'm not gonna be stay at night.. he said I won't be able to enter to Mexico, he printed out some piece of paper and said Sign it, I said I don't know Spanish I have no idea what he has written, he said if I Sign it I'll able to enter Mexico after 1 week, if not 1 year or more, I didn't Sign it because I don't know what he has written, and came back to USA.  My question is, how or where I can check if I'm in blacklist or for how long I can't enter to Mexico??  I'm not interesting for what reason he has written, but if he put for 1 year I'll never go to Mexico again my friends ether, only reason why I'm going to Mexico is a spend money.
— October 28, 2016 2:50 p.m.