to speed up that process, put HALF the stuff back in. if the alarm goes off, take half of that half out otherwise, put in another quarter of the original stuff (eg, half of the half you left out). repeat this with increasingly smaller slices, either taking out if the alarm goes off, or adding if the alarm hasn't gone off yet.
say there were 64 items in the trailer. if you did it one item per day sequentially, it would take 64 days. if you do 32, then 16, then 8, then 4, then 2, then 1, thats 6 days.
in computers, this is called a 'binary search'.