Well, the Cr-48 packages have not been shipped Signature Required, so the driver could have left it on the doorstep, with the door man, etc. Depending on where you live, he may decide it is not safe, and require that someone be there to accept it...
If the tracking number (which should be on the slip) starts with 1ZY318X9... or 1ZA6F803... then it is most likely from Google. Hop onto the UPS web site and track the package to see if it is 6 lbs... However, if it doesn't weigh 6 lbs, and doesn't match either of those tracking numbers, then you have something else coming.