Say I want to look up what I paid for an item, how can I find it's item number?

you neet to sell it to a friend (e. g. for 1 fg)

No, it is something I bought ages ago but can't find in my gold log. Is there another way to find it?

-open the link where u hold the items.
-press f12 in your crome or mozilla
-inspect the element with the item (first button top left of the console)
-you will see there, in comments, a number
-copy that number, and add it to the link "where i = is "(example http://ladderslasher.d2jsp.org/itemHistory.php?i=14773075&c=0)

There is a greasenonkey script so when you go into a profile the item # is clickable and u can see log for it easy. Currently on my phone and dont have my pc bookmarks so can give u it.

in chrome,

right click --> inspect --> scroll to the div with the comment above --> right click --> edit html --> ctrl+c --> ctrl+v in item page url