This was the episode where Desmond first starts time traveling. I believe its when he starts having flashes after the hatch explosion. He goes into the past when he breaks up with Penny and decides that he wants to propose to her instead. He goes to the jewelry store to buy the engagement ring and the jeweler working is Eloise. She tells him that he will not propose to her and that he has to go the island.
Thanks for that - Seems so random - Can't believe you remembered that! Just goes to show you that there are no insignificant bits to this show - everything means something!