I had a guildmate emblemize an item for me. I zoned and now the emblem is gone!
Once the emblem for a guild has been selected, any 20th level or above character (or tradesman of 400 skill or better) can hand the emblemeer a cloak or shield to have it emblazoned with the guild emblem (for a fee, of course).
However, it should be noted that ONLY characters that meet these requirements can WEAR emblemized items as well. If you are below level 20 and 400 skill and you try to wear an item with your guild emblem on it, the emblem will disappear as soon as you zone.
In these cases, NO GOLD WILL BE REIMBURSED. So make sure you wait until the appropriate time to display your guild emblem.