SMS delivery confirmations – are they really deleted? I am requesting SMS delivery retrieval. When they come instantly, it is no problem to acknowledge them. But when they come after e.g. 1 day, it is possible to miss them??

Does android remember the confirmations somewhere?
I'm not sure what version of Android you're running and not quite sure this is what you're asking but on my Ice Cream Sandwich Nexus S if I request a delivery receipt then a little tick appears in the message once it's been delivered. I've got messages from April 18th and they still have the confirmation tick on them so yes Android stores them.

Here's a screenshot of what they look like on my phone: