https://www.buick.com/content/dam/B...pdf/2013_regal_manual_revision 2_20121206.pdf, page 34 of the pdf, or section 2-4 of the owners manual. If you don't require a key for entry, standing within so many feet of the car with the key fob will allow it to lock and unlock. I would place the fob somewhere safe but out of range from the car and see if you can still get in the trunk. With the key fob out of range it shouldn't let you in it. The manual says it's a 3 foot range for this feature.
