extra joker slot, dont know how i got it

[light prism]

all i know about what happened is that it was normal, i used an ecto that hit the negative mime, i had an invis and 3 other negatives, sold the negatives, sold the invis and it hit mime, suddenly i had an extra joker slot

also i dont know if it was before or after i got the joker slot so this might be important, i got another nat negative and bought it before i realised i got an extra slot (the scholar)

fixed because either i sold the mime or picked up a negative popcorn but i would like to know what caused it