This happened to me with these Holophane canopy lights. They are both 175w MV but one of them had a 250w MV lamp installed which was really odd because the fixtures were never actually installed so it's a very interesting mystery as to how a 250w lamp ended up inside a 175w fixture that was never installed. 

Yeah. In 2017, I bought an ITT 50w HPS flood light from a ReStore and noticed it came with a Philips 100w HPS lamp when I took the fixture apart to inspect it. It's funny because the front is latched on instead of held with screws so I could've checked what lamp it had inside while I was at the place.

One of the first HID fixtures I purchased back in 2015 was a GE 250w low bay that was mislamped with a 175w lamp. I ended up installing in the garage at my old house to light it up and it lit up the whole space really well, I always had it on when working on projects. We had to move out and I unfortunately had to leave it there, I got to see the house after it was flipped and they had removed it along with a ceiling fan I had done a custom modern paint job on in the living room. 

I bought this : https://www.lighting-gallery.net/gallery/displayimage.php?album=5198&pos=16&pid=208126 at an antique show and didn't realize it was mis-lamped until I took it apart and saw the H-38 on the ballast .

I bought a Gardco 50w MH recessed fixture at the Restore and when I finally checked to see what lamp it had, it had a MHC70/C/U/MP/4K in it. That's a 70w CMH lamp. With most lights I'll take a peek at the lamp but this one required a allen key to open so I didn't

I once bought a Hubbell canopy light fixture at a swapmeet for $5. The manufacturer sticker on side of fixture denoted it was for a 250 watt MV lamp. When I opened the fixture up, it had a very worn 175 watt probe-start metal halide lamp in it. I then went into the ballast compartment to check ballast, and it had indeed been replaced with a 175 watt metal halide ballast.

If anyone is buying used fixtures off eBay, Craigslist, ReStore, etc. it is always a good idea to check the ballast and confirm it is the proper one  for the lamp in fixture. Once I had bought a used small HID floodlight fixture at a ReStore, and it had a 100 watt HPS lamp in it. I checked the ballast which was made for a 70 watt PSMH lamp. So I replaced the lamp in fixture with proper PSMH lamp. Therefore, rule of thumb: always verify lamp and ballast in a used HID fixture are compatible.

No, since most of my HID fixtures didn’t come with bulbs other than my 201SA that may have its original GE 175 W bulb.

I bought a Westinghouse OV-15 250W/H37 Silverliner that had a very blackened H39 lamp in it...the previous owner probably didn't know any better due to there being no proper labeling.

I've heard of people installing a lower wattage HID lamp of the same type in to save energy, not knowing that HID lamps are matched to a specific ballast. I bought a cheap 100w MV lamp once and one of the reviewers gave it one star for not lasting long in a 175w fixture.

@ Joseph,
Yup, heard of that happening all too often.