SylvanLMP
Easy fix, looking at the tub front you normally will see TWO screws.
Take out both screws GENTLY and pull the cover off towards you.
Hopefully the linkage will be attached to the “stopper” if it isnt dont panic.
Get a wire coat hanger and form one end into a little hook.
VERY SLOWLY and gently try to fish out the stopper (several types) and when you catch it then you can re attach it to the linkage assembly .
If this is an older tub waste replace the linkage, cover plate and stopper with the same brand you just removed.
No need to open walls or floors.
When your putting this stuff back catch each screw before making either one of them tight.
Personally If you want an my opinion you should try to contact a local plumbing contractor and this way they should have the part needed on their truck if replacement becomes necessary.
