Ditto on cleaning out that flametrap. I also have a `93 with a leaking rear main seal. I've been able to minimize the leakage simply by cleaning out the flametrap once a month. So far, the oil loss has been minimal, but I do plan on fixing it eventually. I've been fortunate enough NOT to have experienced cam plug loss. I did install an IPD rear cam plug retainer which should keep me from joining the ranks of the "poppin' plug". :)

The cam plug is different from the rear main seal. The cam plug is at the top of the engine at the back of the valve cover. It does have a tendency to harden and leak. Reach back there and wipe it clean. Drive then see if new oil is there.

The rear main seal is hard to replace check all other possible sources of leak first. Wash down engine and dry, then look for new oil.
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1980 245 Canadian B21A with SU carb and M46 trans

If it's the cam plug you are going to have a lot of o9il leaking, not just a small puddle but a small pool.

To check the rear main, pull the A/T to engine mount on the bottom and look up in front of the flex plate. Mirror and light help. You can see if the oil is comming from the seal area. On my 93 245, I had a rear seal cover bolt fall out and lodge under the flywheel resulting in a uncommanded grinding stop followed by a call for the car trailer to come get the car.

If the area is fairly dirty, shoot a little solvent up that way to clean it out. If you are doing the rear main seal, it's also a good time to do mounts and tranny seals.

The rear cam plug is fairly easy to replace. You can get at it from above, just reach around the back of the head and it is located there, facing towards the firewall. An inspection mirror will help to locate it - hard to see but not toohard to get at once you know ehere it is. This is a common leak source on 200s. I have had them blow out on me more than once (scary - makes a big bang and then dumps oil all over the back of the engine compartment and exhaust downpipes).
Leaks from this location (and others) are often caused by blockage/leakage in the PCV system. If you haven't done so already it would be worthwhile checking/replacing the flametrap and hoses, cleaning the vacuum nipple on the intake manifold, checking and cleaning/replacing the breather box/oil separator. Lots of good info on how to go about all this in the 700/900 FAQ. I know you have a 200, but the engine and PCV system is virtually identical to the NA 740/940, so most of the stuff in the FAQ apples directly to your car too.

Good luck
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Current: '95 945, 95k miles; '90 BMW 325i, 90k miles. Former Volvos, gone but not forgotten '85 245, 250k miles; '91 744T, 150k miles