Actual, real life rules question...

So, we're playing the 11th at Maplewood, and I lose my tee shot a tad right.

It ends up sitting next to a cartpath, inside a lateral hazard but very, very playable.

My stance was on the cart path, and my playing partner seemed to think I could drop (no penalty) as a result.

I played out of the hazard (without grounding the club) thinking that since it was in the hazard, an unplayable or drop would entail a 2 stroke penalty, regardless of the interference of the cartpath.

Could I have dropped with no penalty?

That was my thinking too...

A cart path is an immovable obstruction. 

You might be mixing your two-stroke-penalty with your two-clublengths-relief.

That's right.  The proper procedure under rule 28 (b) or (c) is to drop within the bunker under penalty of one stroke.  If the player drops outside the bunker, other than under option (a), he is in violation of rule 28 and is penalized two strokes.  Then you get into that whole playing from the wrong place business and it gets into "someone call atticus" territory very quickly.

Note: Applies to bunkers only.  Does not apply to WH and LWH.  Rule 28 does not work for you there although 26-1 gives you basically the same options.

Unfortunately, a provisional can't be used in this scenario.  You can announce and play one of course, but once the first ball proves not to be (a) lost or (b) out of bounds it is the ball in play.  You can declare it unplayable at that point but under no circumstances can you short circuit the provisional ball into play.

Under the ROG, yes.  Assuming you wanted to proceed under option 28(a) that is.

This is actually similar to an aspect of the rules that I purposefully violate from time to time.  On Spacey's nemesis hole (par three with water front, left and behind) it's very easy to go long and have your ball disappear.  It might be behind the green in the short rough, in a bunker, or in the drink.  Since it's a regular water hazard there's no drop possible on the green side of the water.  To play completely within the rules you'd have to go up to the green, find out and, if necessary, come back to the tee side of the water.  Don't say it Clive; we'll have no "reasonable evidence" discussion in this thread thank you very much. 

In this sort of scenario we'll at times play a "26-1 provisional".  If we find out the original ball went in the water we wave a magic wand and the second ball becomes the ball in play as if we had proceeded under 26-1a and that was the result of the appropriate shot. 

Completely illegal, wrong, no excuse, and so forth.  However, it beats having your head pounded in by the group behind you on a busy Sunday morning.

This is an example where the "one size fits all" characteristic of the rules presents a dilemma.  You want to do the right thing but the nature of casual, non-tournament golf makes it difficult/impossible.  We end up recording an X for the hole (par + strokes) under section 4-2 of the USGA Handicap System Manual so there's no sandbagging aspect involved but the whole thing leaves a bad taste in my mouth.  There's simply no good solution under the ROG.  I guess I'm, for the most part, a "rules purist" but I'd never advocate wading into a confrontation in your pursuit of the integrity of the game

We wouldn't do this in any sort of competition other than our normal one-v-one bet for a beer.  For example, if the scenario arose during a GHRC round I'd either take the walk of shame or lose the hole.

You may pelt me with rocks now.

If I understand what Uisce had been saying (and the little I know of the rules) once you declare a ball unplayable you can drop. I think where you are confusing things is the difference between unplayable and lost. In your scenario the ball is unplayable, not lost (unless it is so buried that it is completely covered with that "mud"). You can pick up the unplayable ball and drop it instead of a new ball.

Determining a ball unplayable from 120 yards out I guess is possible but sounds more like a Tin Cup moment. There is nothing that says you can't since you are taking the penalty stroke (and in match play lose the hole).