Sent item & item is awaiting pickup?

[hsvcc64]

Hi,
Just after some help and advice here if possible please.
I sent an item to someone who won a "make an offer". I posted the item with an eBay satchel that had a tracking. I keep tabs on the items I send to make sure buyers receive them.

I sent one recently, and since mid last week it has been awaiting pickup from their local post office.

I know it's not my business now that I have posted the item, but I want to make sure the buyer recieves their item. Should I contact them to let them know it's at their local post office incase they didn't receive their little post card saying their item is waiting?
Or is it not my problem now? (I've never wanted to be one of those sellers that once I receive payment and send an item - it's got nothing to do with me anymore)

Only problem is, silly me after I leave feedback for them and send an item I delete it from my sold list. So it's not as easy to contact the buyer this way!
(I also gave the tracking number to them as soon as I posted it)

Has this happened to others before?