What If You Lost Your Paper Savings Bond?

This depends on what sort of paper bonds you are talking about.  If they are bearer bonds - you're usually out of luck.  It might be possible to post a bond with the issuer that they are lost and obtain a replacement.

US Paper savings bonds series EE and others are replaceable.  It is easiest if you have a record of the bond number and the date of issue and better still are at the address that you were at when the bond was issued.  You need to file form 1048.  (So keep a record of the bonds in a separate location from the bonds.  But don't panic yet, there are other ways to get them replaced.)

For full information use the TreasuryDirect.gov web site.  

The TreasuryDirect.gov web site also provides a "Treasury Hunt" database where your outstanding bonds can be researched from your Social Security number.  

"Treasury Hunt may not completely identify any/all savings bonds you may
have lost... Only those that have reached final maturity and were
issued in 1974 and after. To file a claim for lost bonds, you must
submit a Form PD F 1048, Claim for Lost, Stolen or Destroyed United States Savings Bonds, with information about dates of purchase, names on bonds, and other pertinent information."