not all downloads showing

My store only sells downloads. A customer made a purchase and also got a freebie. Paid with IPN (instant). The only link to the download was for the freebie. They immediately contacted me, I changed the status of their purchase from "pending" to delivered, but it didn't work.
I went through the cart system and "bought" the exact same thing. The links were there for me. Did it again, again the links were there.
I checked their order and it only shows the freebie zip available, although the order confirmation email I got has both products listed, and both the products are listed in their order in admin.

What happened here? Any ideas? I am lost. The only difference was that they paid with paypal and I paid with a coupon. Paypal processed the payment just fine, as far as I am concerned - I got their notification of payment.

Thanks in advance.

did you get an order actually generated by zen cart?

Yes, I did. I just knew that the downloads were not showing because the customer wrote me. I went into admin and checked the order, it's all there, but the box that lists the downloads only had the freebie download listed.

I ended up sending the customer a coupon for the amount they spent and they went ahead and got the same product, and this time it worked.

I'd like to find out what the problem was, so I could fix it or prevent it from happening again.

Have you the URL to the Product(s) that they bought that we might peek at?