回这个封条只起装饰作用

the sealer is a paste.  before windshield was put on, the installer used a applicator (like a grease gun) to put the sealer in a shape of strip along the to-be lower edge of the windshield.  when the glass was set, the sealer would seal off moisture/water.  at the end, they put a rubber strip to the groove and make it look good.

if you really want it, dealer has it, or call auto glass companies to buy one.  it's inexpensive. from your pic, if it is still intact, just go get a rubber glue (homedepot has a tube) and glue it back.  it will not affect water tightness.  good luck.