otaku = fanboy
Tsubasa doesn't realise he was at the store that Erika's at?

Piro speaks:
piro didn't recognize her, nor did tsubasa. Tsubasa has not connected that this person who works there is Hayasaka. It is not a plot hole. You keep forgetting the main premise of megatokyo - perception.
Because it was not a situation in which you would expect t find someone like Erika, AND the fact that she is surrounded (in a store like that) with so much other stimulai, she might as well be invisible. Do you really register all all the people that server you at book stores and gas stations etc? No, you dont. Megagamers is a very minor little anime/game/manga/ shop, it is one of hundreds that Tsubasa frequented from time to time. If you only visit a store occasionally, do you really know and remember all the people who work there? I dont think so. To most of us, we interact directly with thousands of people in our lifetimes that don't register on our brains AT ALL.
If you really think about it, its not that hard to believe that tsubasa knows the store, but not the people who work there. Fact is, why doesnt he realize that kimiko is in fact the same waitress that zonked piro with a coffee pot.
thats because people without identities are just objects to us. Sure, i exagerate things a bit, but in a city where an entire block of the city can be leveled and rebuilt without a character even noticing, i dont think its hard to fathom that erika can hide in plain sight because no one expects to see her there.
its always amusing when you folks overthink things :)

Tsubasa speaks:
I believe he is supposed to chase over his first love somewhere in the US. He must have got information through the online otaku communities.
It is true that I firstly told Fred-san that Tsubasa (the character) should not take a major role in the story. However, I'm pleased to see he is an otaku, and he supports Piro (the character) from time to time.