“ So sweetheart, I’ve had an accident and I’m sorry but don’t worry as everything is fine and I’m ok but you’ll need to think about a new carpet and what your like to replace the old stair carpet just give me a couple of days to sort out the insurance claim first”
Sorted. Send me your address and I’ll send you my consultation invoice by return;-)
Burn the house down claim you saw a spider.
Get a degreaser, (spray is better) use a clean cloth, spray directly onto the cloth and rub in clockwise circles from the outside of the stain and work your way inwards.
Come home from work, walk up to the mess and make clear your disappointment with your wife when you state “you’ve missed a bit”. Then put your feet up and watch TV. Works. Every. Time
Is Mexico an option?
"Hi honey, I made a mistake and there is a stain on the carpet. I’ve looked up some options that I wanted to check with you before I tried them to get the stain out. Which of these makes sense?
That one? Great, I’ll run out and get it and get to work on the stain"
I’ve never had an issue just being up front about making a mistake and taking responsibility to fix it.
Ok … back to the serious responses …
I’d accuse my GF of making it … lol
If its not too deep, I’d be tempted to lightly apply this along with some of the mentioned removers…
That or drop a slightly crushed Mascara bottle and wand near the stain! 
just remember that once you’ve cleaned it, you will also need to buy a new bike! You need to make sure it doesn’t happen again by using the bike with the dirty chain…
Or use Molten Speed Wax, no oil needed!!
Genius 
In Soviet Russia, WIFE save YOU!
I like this idea 
Tell your wife that your girlfriend did it 
This.
Or degrease and chemically dry your chain and start using Squirt. Either way, no more grease marks.
While loading my sons bike in the back of my car, we managed to get chain grease on my cloth seats.
This removed it completely. Absolutely wonderful stuff.
Sleep with her sister and I guarantee she won’t care about the carpet stain
This has all the making of Thread of the Year…
This might be too late but I had a similar experience driving back from a Gran Fondo this weekend. My bike was in the back of the SUV and my wifes white overnight bag fell over onto the chain. I ended up spraying on Simple Green that I use to clean my chain and wiped it down with a damp cloth. Worked perfectly and the bag is as good as new.
Buy a puppy immediately …