Someone stole my wheel center caps - Do I need to replace them?

Did you call the place that did your tires? At least ask if they had your center caps? That's quite a coincidence to assume it was probably just kids. I'd at least make a phone call, not accusatory, just ask if anyone happened to find or put aside a set of center caps. Nothing to lose in asking.

 

The reason that Costco may have removed the front wheel center caps is if they put the wheels on the tire balancing machine as part of their tire rotation service.

The caps serve a cosmetic function and can be replaced or not, at your option.

If I was a kid, Prius wheel caps would not be high on my personal list of items to steal.

 

That and there really hard to take off from the outside. You'd have to spend alot of time prying them off. Really hard as there flush. But from the back they just pop off so yeah you have a terrible tire shop. Its really noticeable there missing. Impossible not to notice after tire service.

In the future when any work has been done to your car take a second and look at where the car was serviced. Under the hood....I drive away a bit and pull over and pop the hood...unless like me one day long time ago I was having my new sentra serviced for a recall notice...on the walk around noticed my hood wasn't closed. It was ajar. Found fuse box cover missing and tools on the top of the engine.
Once on another much nicer car specifically asked the balance weights not appear on the outside of the wheel. Guess where they were?
Back up on the rack it went.
Any tire work look at the tires before you drive away. See if they torn up the mags. Valve stem caps missing etc.
And especially without a doubt any dealer service done look under there. Nothing would surprise me.

 

Brake fluid changed? Check if the bleed caps are still present.

I taped my phone number to our lock nut socket.

 

When I was in 5th grade I attended a school that was across from a medical facility.
It was probably a aspect of great annoyance to the Doctors and people parking there, but part of the "game" many of my friends liked to participate in, was taking the caps off tires. The more expensive the vehicle the more prestigious.

I swear, I never did it.

But I do remember it being something many kids did.

So my point being? You never know what kids will steal.

 

yep...years maybe 100 kids used to steal hood ornaments. Dating myself.

To the op's question leaving the cap off exposes the big castle nut to extreme corrosion. That big nut basically holds the wheel on. Even protected by the dustcap it will get really rusted. Without the cap it could be become hopelessly corroded to get that nut off and may damage the threaded end of the steering knuckle. That nut needs to come off to repair a bad wheel bearing which is a common malady on a G2 prius myself included. To exacerbate any further corrosion I pack that hole with grease and then pop the cap on back on. Grease cant go anywhere as the rim of the wheel seals it in and it will prevent that nut assy from becoming hopelessly corroded.. Plus it also prevents the wheel from being welded on to the hub which is a really well known issue with the G2. Grease in that hole then sealed will help prevent that.

So yeah in short really bad to run without that dust cap.