Do people here go without insurance on their older pop up truck campers? Is there a liability concern? I'm not really concerned about physical damage since the camper itself is not worth that much.
The "Liability" insurance for the camper will be extended from your truck insurance liability coverage/policy when the camper is mounted on the truck just like when you attach a trailer to your vehicle. In most instances your Homeowner's policy may have a section that extends liability insurance coverage for your camper when the camper is NOT mounted on the truck and sitting on your home property. READ your Homeowner's policy to find out.
If the camper will sit parked elsewhere away from your residence such as a storage lot you could have a liability issue if for instance the camper fell off it's stands and damaged another person's property or even worse injured or killed another person. Your homeowner's "MAY OR MAY NOT" extend liability coverage to the camper when stored on a storage lot. Once again READ your Homeowner's policy to find out.
I always say when having insurance policies quoted and BEFORE you purchase that insurance policy READ THE POLICY AND UNDERSTAND THE EXCLUSIONS! Exclusions are written into an insurance contract to specifically EXCLUDE what the insurer WILL NOT COVER. If you don't understand the insurance contract as it's written/presented have the agent or better yet your attorney review the policy and explain the "Terms, Conditions and Exclusions" to you in language you completely understand that way you can determine what type of coverage you are purchasing to make sure it meets YOUR needs.
I suggest you re-read that $344 quote for the camper and see what the policy actually covers and what are the "Exclusions" listed in the policy. Most insurance reps are not that well versed in RV coverage policies no matter what they say as YOU have already found out. This $344 premium may not be VERY HIGH in my opinion for a Non-Towable/None Drive-able truck mounted camper IF it is a "Full Coverage" policy on the camper itself HOWEVER the only information you have provided us concerning the policy is PRICE and without you knowing and telling us the coverage's and exclusions listed in the policy it's impossible to determine if this is a good policy or not.
If the value of your truck camper is very low as you stated I would not buy "Collision/Physical Damage" Coverage on the camper as you will never get the value from the policy versus the cost of the policy on a cheap camper. I "Might" look at "Comprehensive" coverage if it was cheap. That would cover you for the next time the hail storm ruins the roof of the camper.
The need for or against a separate liability policy on your camper would be my major concern depending upon what your Homeowner's policy Will or Will NOT cover from a liability perspective when the camper is NOT mounted on your truck depending upon where you have the camper stored.
I completely understand why your insurer NOW wants 2 separate policies on the truck and the camper as the truck was not originally manufactured as a motor-home and as such is probably not licensed and registered as a "Motorhome". What you have is a truck upon which you have mounted a removable camper body. You were fortunate they paid the claim for the damage to your camper as your agent certainly did NOT do his due diligence when originally writing your insurance policy for your truck and your camper.