Has anyone ever experienced a PL out-ranking the CO?

That is the absolute wrong answer based on given infornation. The Senior regularly assigned officer or a Captain assigned by the Battalion commander should be placed in temporary command. Unless those senior to the 2LT are otherwise ineligible. I doubt the entire Company's compliment of officers are in eligible unless something crazy happened. So given 600-20 para 2-8a(1) and (3) the senior LT should assume command. The 2LT can still be leveraged as the XO to ensure the trains run on time. I have seen the BN CDR in communication with the BDE CDR assign a new Commander as professional development for underlaps less than 12 months to accommodate timing in slating. It was for an MCT. I've been a PL and acting Commander. I was a 2LT but all other LTs were on block leave. I may have been the last standing officer in the Troop. I've also seen where the Senior officer in temporary Command changes command with the incoming after several months; and reverts to Company XO. Special care must be taken to ensure the change of command inventory is cleaned up and responsibility properly affixed for losses.

If we are talking an HHC (it was unclear from the original post): I've also seen where in a HHC the BN XO or CDR identifies a staff officer to assume command. Especially in this case where the temporary Commander will change without the return of the previously assigned commander. They would do this if for no other reason to ensure the primary Hand receipt is straight. Given para 2-8a(2) below, the next eligible senior Captain should be placed in command. Arguments could be made to install a non-Command Complete Captain who,is next in line

I've seen an SMP Cadet Assigned as a AT Infantry Company XO for the same reason but a senior PL would assume command. They used his XO-ness to coordinate logistics, as a knock around guy to run errands, and otherwise make stuff happen to keep PLs on the line.

AR 600-20
"2–8. Death, disability, retirement, reassignment, or absence of the commander
a. Commander of Army element.
(1) If a commander of an Army element, other than a commander of a headquarters and headquarters element, dies, becomes disabled, retires, is reassigned, or is temporarily absent, the senior regularly assigned Army Soldier will assume command.
(2) If the commander of a headquarters and headquarters element dies, becomes disabled, retires, is reassigned, or is temporarily absent, the senior regularly assigned Army Soldier of the particular headquarters and headquarters element who performs duties within the element will assume command. For example, if a division headquarters and headquar- ters company commander is temporarily absent, the executive officer as the senior regularly assigned Army Soldier who performs duties within the headquarters company would assume command and not the division commander.
(3) Senior regularly assigned Army Soldier refers (in order of priority) to officers, WOs, cadets, NCOs, specialists, or privates present for duty unless they are ineligible under paragraphs 2–15 or 2–16. They assume command until relieved by proper authority except as provided in 2–8c. Assumption of command under these conditions is announced per paragraph 2–5. However, the announcement will indicate assumption as acting commander unless designated as permanent by the proper authority. It is not necessary to rescind the announcement designating an acting commander to assume duties of the commander "during the temporary absence of the regularly assigned commander" if the announce- ment gives the time element involved. A rescinding announcement is required if the temporary assumption of command is for an indefinite period."

Well, that is unusual, certainly, to say the least...I've never seen anything like that, I've never seen anything like that, of course...though, one might logically think those higher would ostensibly be aware of the whole thing...supposing, as you say, that their personalities mean well, I suppose it could work, I'd gather, though, as you pointed out, the circumstance is, if nothing else, odd, clearly, you know?

This should never happen anywhere, unless the other LTs have personal reasons why they are not able to meet the commitments of the job. Bad example for the unit. Thank you for your service.