If it has miles on it since the spark plug broke, chances are the electrode isn't in the cylinder anymore. However, it would be a good idea to use a bore scope to inspect inside the cylinder for damage or pieces of the electrode.
If by some chance the electrode is still there, you should be able to remove it with a small mechanic magnet through the spark plug hole.
As far as the compression, a leak down will help determine if there is an issue. And yes, if the compression is low in the cylinder, it can cause a misfire. Have you tried getting a compression tester at a parts store? Most will lend one to you at no charge.
When the truck is running, is it a constant cylinder 2 misfire? In other words, do you feel it constantly when it's running, or does it only happen under certain conditions? Let me know.
Also, here is what I feel needs to be done at this point: First, ask your mechanic if he has a borescope. If he does, have him check inside the cylinder for damage to the cylinder walls or evidence of any damage to the valves. If there is anything in there from the old spark plug, see if it can be removed with a magnet or even a vacuum supply via a pump and flexible vacuum hose.
If that can't be done, then the compression needs to be tested.
Here is a link that explains how it's done:
Below, I attached the directions specific to this vehicle. The expected compression is provided, and it indicates the lowest cylinder compression should not be less than 70% of the highest. If cylinder 2 is below that, try a wet compression test. Basically, put a small amount (about a tablespoon) of oil in the cylinder and recheck. If the compression increases, chances are the rings or cylinder walls are worn. If there is no change, it is likely a problem with a valve leaking.
Let me know what you find or if you have other questions.
See pics below.
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Wednesday, March 22nd, 2023 AT 6:51 PM