Sorry if this feature may already somehow be in place and I just haven't seen it.. but I think it would be simpler and easier for both buyers and sellers if either:

a) the user trading the items or auctioning the pet(s) had a link that would take you to a page that listed all trade lots or all pets that person had in auction.  for example, the links would look something like this in the same section as the other links -

View Merchant Shop

View Showroom

View Gallery

View Rancher Shop

View Party

View Item Trades | View Item Auctions

View Pet Auctions

and those links would bring up corresponding pages with any trades or auctions that person had in a list, from which you could either make an offer or bid. does this make sense?

(this setup would also allow users to make use of the pet search function and actually be able to bid on a pet they're interested in without having to first manually look through a lot of auction pages.)

or

b) create a search engine in both trades and auctions so a buyer can enter the seller's username, which would bring up the same usable page as mentioned above.

Again I really do apologize if something like this already exists and I'm not aware of it.  I just thought something to this effect would make it easier to find a pet or item someone has advertised without having to manually search through a ridiculous amount of pages.

I totally and completely agree with this idea.

As a little add-on, maybe a search for a certain pet or type of pet in auctions, because when you click on the pet auctions page in the pet search it just takes you to general auctions and you still have to find the pet. But that part isn't as necessary, I totally agree with Starlet's idea.