This is the 7888th most frequent Polish word.
miszczaka
"Miszczaka" is not a standard Polish word; it could be a misspelling, surname, or colloquial term.
In this context, 'Miszczaka' is the accusative case of a proper noun, used to denote whom I saw.
Miszczaka widziałem wczoraj na rynku.
I saw Miszczak yesterday at the market.
Here, 'Miszczaki' is in the genitive case, indicating possession or association.
Nie zapomnij o poradzie od Miszczaki.
Don't forget about the advice from Miszczak.
This usage shows 'Miszczakiem' in the instrumental case, specifying whom we will talk with.