Misplaced tyre lever - alternatives?

Um... buy a new tyre lever? They're so cheap they're practically free.

OK, that doesn't help you this time but buying three or four tyre levers means there shouldn't be a "next time" for quite a while.

1. Try to pull it by hand

In case your outer tube is not that firm, you're often able to remove it by hand. First, put the opposite side of the valve on the ground, massage the tube down so you get slightly more flexibility there. Next, put the valve on the ground, squeeze the tire firmly, pull it back a bit and try pushing very hard to get it over the rim. Video description by Bike Rader

2. Use the quick release

Depending on the exact shape, you could try to use the lever of your quick release. This highly depend on the lever but is definitely worth the try in your scenario.

3. Bend some plastic

If you're home and have access to other tools, you might be able to bend some plastic (eg. old toothbrush). More details ons Instructables, but this is of course not possible while on the road.

Prevention is the best cure. I know it takes 2 tyre levers to deal with a flat on my road bike, so I carry a pair of decent ones (with some silver paint on them so they show up better by torchlight). In addition I carry a third, old and worn but known good, because I've been known to snap plastic tyre levers (luckily at home). They can also ping off into the middle distance so a spare is no bad thing. I might swap this third one for a metal lever if I can find the ones I've got tucked away somewhere. Even if you could find (hard enough) wood, carving one requires a reasonable knife, which isn't part of a standard bike tool kit, though it is part of mine.

The fallback is other riders. I'm sometimes out solo at all hours hence why I go so well equipped (though rarely to the extent of carrying cutlery) but on many of the rides I do there are other riders on the same route. Some of them are likely to be with or behind me even if most are far in front. Even riding solo there are likely to be other cyclists around during the day.

Any rider can be struggling with a mechanical, and that's why you should slow down and check that a rider standing by the roadside is OK: one day it might be you, and looking after each other is the right thing to do anyway.

As kids we used the flat end of a screwdriver to get it started then stuck in a spoon. Moved the screwdriver along a bit and levered a bit more off etc. Just try not to stab the tube, lol.

At home I'd use a screwdriver. If you are out in the field and don't have a screwdriver, 9mm quick release levers work quite well and you bike already has two of them:

EDIT: As pointed out in the comments and some of the other answers, screwdrivers are not a good idea. You risk scratching the rim or puncturing the tube. Only do that if really need to, and be very careful.

On a mountain bike tires are usually soft and large enough to be able to use the "squeeze and bend" technique.

Like here

Edit I see that it's not limited to mountain bikes:

For replacing the tire you need a pump, so I assume you have one. So you can use this part of it as a lever:

Used it several times without any problems.

On a recent bikepacking trip I had a flat and discovered I forgot to include my tire levers in my repair kit. I had a tube and hand pump. I used two pliable plastic cards I could sacrifice as a substitute.

I folded each in half length wise and used them like levers. I bent the first one between spokes to allow space for the second one to do its job. In hindsight I could have tried the titanium sporks we had.

I don't know if this would work on all bike tires but it did work on a gravel bike with a 640 x 42 tire.