Hmm that is pretty annoying... I don't know if there's much we can do about it but I'll make sure the admin is aware. Hopefully we can at least get the ability to look at old posts back!
Temporary solution: Use google advanced search.
Search for "Plastic Wallet" site:pokemonelite2000.com/forum
This brings up all mentions of Plastic Wallet on PE2K.
Search for "Plastic Wallet's Avatar" site:pokemonelite2000.com/forum
If you just want to find posts that you've made (not people mentioning you) try this search instead. The text "Plastic Wallet's Avatar" is inbuilt into all your forum posts.
Anyone else can use these, just substitute your username. Hope this helps for now!