The "seen + date" tag has disappeared from one of my facebook conversation's last messsage?

[saucier]

The last message of a conversation with someone always has the "seen + date" tag under it (or sent + date for that matter, if the person didn't read it).

The last message of the conversation with my ex girlfriend who deleted me on facebook (but didnt block me because i can still find her and also i still have the add friend and message button) doesn't have the "seen + date" tag anymore. It had it previously. Does it mean she deleted the conversation ?
AbraXus. Thank you for answering but actually you re wrong because I made a test. First of all, my oldest conversation still has this tag, and it's from more than a year ago. Also, I made a test with a friend a it actually deletes the tag from one party when the other party deletes the conversation.

[abraXus]

no, it just means you havent talked to her recently - the seen by thing doesnt stay there forever