You could try using the key for starters...
A torch
Go to the dealer with your ownership and have them make you a new key!
remove rear seat and insulation
To open the trunk on a Buick LaCrosse without a button on the door, you can use the key fob by pressing the trunk release button. If you don't have the fob, you can also access the trunk using the key itself, inserting it into the trunk lock. Alternatively, if the rear seats fold down, you can reach into the trunk from the cabin.
On the 1985 Caprice the logo emblem in the center of the trunk swivels up and out of the way revealing the keyhole.
cHECK THE FUSE IN THE FUSE PANEL.
NO, only button it has is on remote and manual open on trunk door, when car is unlocked.
press the door lock open or lock for 5 seconds.
Have you tried the trunk lock button inside of the glove box? Greg
Bottom half of instrument brightness control
try taking out the back seat. that is how i got into my 84 buick lesabra to unlock it
Hold the power door lock switch in the "unlock" position for a few seconds and you will hear the trunk open. The truck lid does not pop up, but it will be open.