attic shower p trap

I hired a plumber to lay the water and waste pipes in my attic for a new bathroom. He set the toilet, vanity (vented under the sink) and shower base. He left a message for me to keep the shower base drain covered because there was no room for a p trap.
My question is: don't all plumbing fixtures have to have a ptrap? Or will this vent under the sink vanity work with shower.
I don't want to call the plumber back because it ended up costing me $800 more than budgeted, PLUS, a faucet was broke, down stairs toilet became "unseated" and the water intake to my water heater broke, all while he was left in the house by himself. He fixed the faucet, but I fixed the rest.
This is my first house I bought on my own, in a new town, so I don't have many family/friends to help me.

You are correct, all drains must be vented.

Did he/you get a building permit? Was the guy licensed? The only drain that doesn't need a trap in the floor/wall is the toilet, which has one inside it. Relying on the user to seal the drain in a shower to prevent gas leaks, etc. is criminal in my view...the guy shouldn't be a plumber, and if he has a license, he must have gotten it in a cracker jack box.

Do you have details of the shower drain situation? Is this on a slab, a second floor, the ceiling finished underneath? Although it may not look good if in a ceiling, you will need to run the drain through a chase if it needs to be lower than the ceiling above. If it is in a cement floor, you'd need to break up some concrete. If the discharge is higher than the pipe needs to be, there are ways around that, too, with a sump and pump system.

trap

It is in the attic so not likely to have any concrete to break. But there is always a way to provide a trap, and relying on a piece of rubber over the drain to provide the seal, implies that this was a very inexperienced handyman, not a plumber. I hope you have not paid him yet. If so, you might want to call the city inspector and have him impress the "plumber" about the correct way to do things like this.

Did this guy install a waste pipe down to the second floor to connect into a main stack; or did he drain the entire bathroom into the vent stack coming up from below? You should have a plumber take a good look at this whole project.

attic shower

I really appreciate all the help.
After reading the replies, it sounds like I will be pulling up the shower pan today and figuring out a way to install a ptrap. I am lucky, my shower is upstairs over the kitchen (which will be diy remodeled soon) so I can hopefully fit a trap through the wooden attic floor. If that fails I can go through the kitchen celing.
The shower drain is tied into the house's main waste pipe, going directly to the septic.
The upstairs bathroom was/is a diy project but I got stuck trying to figure out how to lay the waste line, so I relied on a "home improvement warehouse" recommendation for a "plumber". It didn't need a permit since it was diy and labor was budgeted at less than $500. I just assumed (yes, I know) that the "plumber" recommended would be a real plumber and I didn't even ask about his qualifications.
My late husband was a "handyman" and I have absorbed more knowledge than I thought I knew, but I am never "sure" about plumbing.
Thanks again

If this "plumber" works for a company, I'd call and complain....and LOUDLY! First of all the p trap issue. Secondly, it sounds as if he tied this attic bathroom into the vent going out the roof. At the point it goes higher than the highest existing fixtures, it was a stack vent, not a waste stack. Third, your shower may not even be vented. Fourth, you stated the vanity was vented "under the sink". I would assume from this statement that the vanity is vented with an air admitance valve. If AAVs are even permited where you live, a good plumber would be able to vent the vanity (as well as all the other fixtures) correctly.

People who do shoddy work like this and call themselves a plumber absolutely chap my ass! Get your money back, complain to the company he works for as well as to the "home improvement warehouse" who recommended him. If this "handy butcher" doesnt want to give you your money back, take alot of photos of the abortion he installed then take him to small claims court. There is no reason in the world you should have to put up with this mess!

<sorry....can you tell I havent had my coffee yet? >