Does anyone have a prada with nothing on the zipper? I just returned a bag to a Resale shop in LA because of this, as I think it is fake. They are going to refund, but say the seller insists the bag is authentic and is having it authenticated. They say this seller often sells high end bags through them and this has never been a problem.
Usually the YKK zippers just have the YKK mark on the SIDE of the zipper with nothing on the head (usually, the LAMPO or RIRI ones have this marking on the back).
Overall, Prada's use of zippers is a little confusing and I don't think there is a standardized system for it. I think it depends on 1) the season/collection and 2) the factory where they were made.
For example, most of my Prada bags use Lampo, a few RiRI, and one or two IPI. One of mine with IPI zippers is the short handled Prada shopper tote that is reproduced in the "nylon essentials" EVERY season. I got mine four years or so ago, but this summer saw the same model in the Prada boutique, but now it had RIRI zippers.
Likewise, my top-end Prada items usually use RIRI, but this too isn't always the case. I have a black luggage piece that is several years old that was one of the most expensive nylon items (about twice the price of the regular nylon items and only distributed in the main boutiques), and it has LAMPO.
It was my belief that the YKK items were used for the entry-level, cheaper bags, Lampo and IPI for the midrange, and RIRI for the top end (for example, my Prada produced Jil Sander items use RIRI). BUT, again, this isn't always the case. I have a Luna Rossa bag, made in China, that retailed about 1/10 what the mainline bags run and it has LAMPO zippers. Finally, I have a vintage nylon piece from the mid 1990's, back before they even used the triangle heavily (it has an embossed "PRADA" on the leather accenting), that has perhaps the best quality and workmanship of any of my bags. This bag uses YKK zippers.
So, overall, it's hard to judge just from the zippers! Maybe the factories just have a bin of zippers that they pull at random (haha).
With your bag, look more closely at the zipper and see if you can find some tiny mark on it; chances are it is probably YKK. Some of the fakes use YKK, too, but some of the auth bags have them as well.