If the meat was difficult to ID, they may have been Al Pastor tacos. Lebanese immigrants to Mexico created a wonderful fusion of tacos cut from the beef / lamb shwarma style meat that gets roasted on a vertical rotisserie spit.
Al pastor may be cooked shawarma-style on a trompo, but the meat itself is definitely pork. You won’t be eating tacos al pastor and wondering what the “mystery meat” is, the look and flavor is very distinct. It was probably ground beef in those mini tacos.
Was the meat ground or sliced? There’s a Middle Eastern style of “tacos” that I love which is essentially ground meat (beef or lamb, I suppose) in a savory sauce spread thinly over flat bread and toasted in an oven.
There are some places here that do the small ‘street’ tacos on corn torts. My favorite is a nearby place that makes birria tacos. Birria in Mexico is usually goat, but here it’s shredded beef in a tasty broth. The torts are dipped in the broth and fried on the grill before being loaded with good stuff.
Yesterday I had deep fried shrimp tacos on corn torts at a different restaurant. Good stuff.
You just reminded me of the episode of Hill Street Blues where Howard Hunter took a date to a South Asian restaurant that was caught serving cat meat harvested around the neighborhood. Good times!