if your shower is raised a little, say 200mm, then the trap is behind the panel that covers the gap, like a shortened version of a bath panel.if not then its a shallow trap under the floorboards and there is no easy way around ir.
i had this in an ensuite in the last house where the shower and a hand basin shared the waste outlet at a tee and this gunged up with hair(10 yrs worth)and the only way was to locate it ,split it and clean it out, about half a cup of gunk/hair etc.
the signs were smells,not too bad but it took ages to drain the water after a shower and a glug glug noise sometimes as one waste slowed the flow of water from the other. i notice it now in my new home at the sink where the whiff of smells can be bad. too many outlets sharing the waste pipe resulting in trap seal loss as one emptying can pull the water from the main trap and allow odours back up the plughole. in this case i will install extra wastes but you will have to get some floorboards up or rod it with a flexible rod down the plughole (looks like old fashioned curtain wire, stiff but flexible)