As most people have said, it is highly unlikely that you had anemia. You would have shortness of breath and a high heart rate. It is more likely that you were experiencing some dehydration. By the sound of it, you were drinking a lot of tea, which is a diuretic and would cause further dehydration. Also dehydration can cause your stomach to feel uneasy, and you can have nausea/vomiting, which is why many dehydrated people are unable to tolerate oral intake and receive IV fluids.
However, there are some other concerns. Anemia is mostly caused by blood loss, certain deficiencies, genetic causes, and hemolysis. Vegetarians and vegans often do not get enough vitamin B12 which is needed for DNA synthesis. This causes the red blood cells to become enlarged. However, you would notice other problems with B12 deficiency including neurological changes, fatigue, and other symptoms of anemia without even exercising. This does not happen in an acute setting. So, I don't believe that you were experiencing symptoms from B12 deficiency.
Another cause that can occur is hemolytic anemia, where the red blood cells are being damaged. In rare cases, there have been times where excessive damage to capillary beds, such as repetitive pounding on your feet when hiking, that could cause trauma to the red blood cells. Although it can be profound, this kind of hemolysis is usually mild, and you shouldn't experience many symptoms of anemia, but what you might notice is blood or a pinkish color in your urine. This is a very RARE, and most people have other problems like vasculitis.
So, next time you go out, I would suggest proper nutrition and hydration. Try to avoid tea as it will further dehydrate you.