I find it hard to believe you couldn't engineer a solution to muffle the sound. Assuming holding down the power button to turn it off didn't work (like, you know, every other phone and tablet ever) you could shove it under your mattress, in the freezer, put it in a ziploc and submerge it in the tub/sink, go throw it in the trunk of your car, stick it in a parcel and mail it to the owner...