Does trunk have a place for key to manualy open trunk

No. Still looking for information if you are having trouble getting it open, but if you are looking for a hey-hole on the deck or near there is none

I found this, in case you don't already know: Location of the trunk release: activating the release requires depressing the door lock for two seconds with the shifter in Park.

http://www.vadengmpp.com/owners-manual/buick/2005-Buick-Lacrosse.pdf Chapter 2 Page 13. Later model years have a key hole above the license plate but not 2005. Remote fob, the procedure above, and the Emergency handle inside the trunk if somebody got locked in.

Once you have trunk open, install an emergency cable for opening trunk during a system failure. Attach a cable to the existing manual-pull emergency cable in the trunk lid and feed it up through and attach the other end to the child safety seat fitting at the top of the back seat. During system failures, this will allow you to open the trunk lid. I saw this idea on another site :)