I have explained how this works. There is indeed a delete box at the bottom of the editproduct screen
Here is the code right at the bottom of the editproduct template that confirms this
Code:
Content visible to verified customers only.
So lets break down that if clause.
1. USER DELETE MUST BE SET TO YES IN admin => admin options
$Globals['userdel'] == "yes"
2. The ad must be a regular ad.
$isauction == 0
3. The ad if an auction must have no bids on it to be able to be deleted
$isauction == 1 && $highbidder == 0
Now based on my explanation of how the program operates to show a delete box what case is yours here? The delete box is only not going to show in two cases. One you do not have users able to delete ads set in your admin options or this is not an ad but an auction and it has bids on it. Here is a picture to show what I see using the default 2.6 code