Run the coil test.

If it does not fling out, then don't worry about it.

It will return again in your next high score....

Shine a flashlight under the plastics and plastic ball guides. Look behind rubbers.

I had frosted LEDs in the sling spots on my MET pro that would fly out at least once a week. I solved that problem by removing the frosted caps on the LEDs. Now they stay in just fine without that rounded bulb end - no need for glue.

I once went to service a Whodunit that had a ball missing error and never could find it.

Not under the plastics, not in the cab, not in the harness. 80grams of steel literally evaporated.

Machine is pretty much toast. Pull the plug and don't play. It's trash but I'd give you 1k to cover parts if you cover shipping

At the VFW Showcase last year this happened twice (yes TWICE) on the same WH20. Rum-Z and I, whom both own WH20s and know all the places it could have gone, searched for a long time and never found either.
*POOF*

Larry just puts a piece of scotch tape over the face of the spot light. haha. I am so glad stern finally came out with brackets that hold the spot light flashers and bulbs in now. So nice.

Lift pin overhead and shake. It's like getting a guitar pick out of an acoustic guitar.

It's a crummy design and they always fall out. Should have used a bayonet style or something.

You want to remove it if you find it ASAP. It'll turn up. On stern's the biggest danger is that it falls into the trough, rendering the game unplayable until removed.

I recommend checking the ball trough too. One time I saw one in there and you could only see it from one specific angle.

Did you check the ball trough? That's were a bulb ended up in my ST. Never saw it fly out.

I once had a bulb slip through the ball trough and under the apron. I Didn't find it until I lifted the playfield.

I just picked up a barb wire recently--when I lifted the playfield before moving it, there were 6 balls lost in the rear of the cabinet and 4 in the trough. It is a 4-ball game.

What an anticlimactic ending to an otherwise promising thread

I lost a bulb before. Game had a shaker. About a month later I finally found it at the cabinet bottom.

Shaker 4 teh win!

That happens a lot with pf screws...

Don't keep playing with parts lying on the play field!(Unless you're well on your way to a high score--then suffer the consequences!)

I still want to know how a ball disappears! That's crazy!

Since we are past all of the serious answers.

Only if the bulb that is rolling around is scoring more points than your normal ball in play is.

How can you be sure it wasn't a different bulb you found?

This should be a required mode in every "magic" themed pin.

I have a DrWho, and did the "USB Tardis" mod. A few weeks ago I'd a monster game going when during a dalek battle, the friggin' ROOF popped off the USB tardis and plopped right smack in the middle of the pf. Woulda been hilarious (if not almost appropriate!) if it didn't make me flub the multiball... but I managed to panic-cradle the last ball, then called my 11yo daughter and instructed her how to open the coin door and remove the glass, extract the not-yet-destroyed roof, replace the glass and shut the door without titling (the last part being tricky on this machine) while I held the flipper...

...she made a right proper companion in that respect

Unfortunately I came up just short of my GC score.

It once happened in my TOM. Ball goes in trunk, then a thunk, then ball is missing. Found it in the bottom of the cabinet. It took me like 10 minutes under the hood to figure out how it happened, turns out that it is just possible for the ball to get over the edge of the trough near an insert. I mean just possible. Like the ball had to somehow bounce in a spot where it doesn't look like anything should cause it to bounce, and if it had bounces like 1/100 of an inch different in any axis, it could not get out of the trough.