For reference, the vehicle is a 4WD 2013 Toyota Tacoma. It has factory plastic fender flares.

I backed over an unseen rock and knocked off my right rear mud flap / mud guard. It's not broken too badly at all and I think it will go back on more or less securely.

The three 10 mm bolts / screws will be easy to replace / reattach, but I am not familiar with the three plastic "push pins" (for lack of knowing the proper term).
1. Do you buy them at the Toyota Dealer?
2. Do you just push them in and they reattach into an unseen receptacle like magic?

Any help is appreciated.

I did the same thing with my 4Runner on a mound of frozen snow. As noted, the flap is secured with a combination of steel bolts and plunger type push-pin gizmos. After removing the flap to determine the extent of the damage, I discovered that not only were a few of the push-pin gizmos pulled loose, a couple of the plastic inserts for the steel bolts to thread into were also pulled from their mounting holes. Figuring these were both single use fasteners, I ordered new parts from Toyota then reassembled. Tip: When installing the plastic inserts for the steel bolts, examine the original holes for damage and rotate the inserts 180° from their original orientation. This will give the two tabs on the insert something to bite into.

L: Insert for steel bolt. R: Plunger type push-pin gizmo

Thanks HJS, that is very helpful. Just seeing the parts gives me a much better idea of how they are installed.

I will go see my local dealer and order some.

Many thanks. As usual, this forum always comes through!

Sometimes you can reuse them.
Pull the center up and it falls out, push it in to secure it.
New ones are cheap. https://www.autobodysupply.net/W-E-3362-p/w-e3362.htm

Pep boys stocks them by the body work area if you need a couple.

Don’t need to disassemble to remove. Just pop the center plunger up to release the expansion

Same thing happened to me with my 2011 Tacoma except it was one of the front mud flaps. Ripped the part of the fender they attach to apart so that it can not be reattached. One of the rear mud flaps just disappeared. No idea what happened to it. Ordered another one with those plastic things in shown in hjs157's post and installed it with no problem. Plastic attached to plastic with plastic. Grrrrr

I got my new pushpins online from a Toyota parts place (a dealer selling on the Internet). First, go to ToyoDIY.com, create an account and enter your vehicle. This gives you access to the EPC (electronic parts catalog), with handy drawings of each section of the vehicle, showing each part with its part number, and the schematic shows how/where it goes. Having the part number (pushpin in this case), throw the number into a search engine and you will find lots of places to get it, sometimes even Amazon. If you order from an online dealer, expect to pay as much for shipping as for the small part itself. Better to find a couple of other things to order along with it, to ease the shipping cost pain. I usually get a new set of OEM wiper arms/blades.

If you have a Lowe's nearby, they also have a small automotive section that has the plastic push pins.

Pretty sure this is what you need.
https://parts.olathetoyota.com...VhcmNoIFJlc3VsdHM%3D

They are quite longer and slimmer than the ones you see holding the trim under the hood.
If in doubt, just show the parts guy the vehicle itself and he will get what you need.

Or

https://www.amazon.com/Mudguar...Runner/dp/B0BQ1X5YYY

My rear flaps are currently held on by just the bolts on my 2015. The only issue I have is where the mud flap meets the fender flare. Due to the movement of the mud flap, it has worn off the paint on the fender flare.

I went to the local Toyota Dealer and ordered the "Plastic Push Pin Rivets" (Toyota simply calls them "Clips"). I needed an extra one for the other side, since it is mysteriously missing just one. I better check and see that the screws are snug on that side.

For the other parts, I will see if what I have is still serviceable. If not, I will order knock-offs from Amazon.

For a good fit get exact replacements from your toyota dealer, since none of those plastic clips of any kind from any brand of car are standard. All those guys are 200% proprietary. Any other solution has a 95% chance of 100% frustration.