Actually, the question should be spelled:
Wo ist mein Capitan?
Wo means where.
ist is the properly spelling for the active form of "to be."
Blame it on 3 years of German. But, that was about 40 ish years ago.
One time, around the turn of the century, friends and us were eating dinner at a place called the Bavarian Bar and Grill. I ordered the meal for my wife and me in German. The waiter repeated it back in German for confirmation and, I, without thinking and working for decades in construction in Texas, said "Si."