I'm experiencing the same problem. I'm not sure where surveys are stored. Hopefully in the SQL database (in part).
I've just rolled back my installation to 1.92, exported surveys to both Limesurvey and Xml formats - will then roll forward and import them each.
Thankfully I only have a handful of surveys. I'm sure there must be a more efficient way to do this. Someone please help.
Addendum:
Minutes later - having upgraded a second time to 2.00 - I still cannot see all the previous surveys. However, links to previous surveys in 1.92 format are still live. So it seems that the old surveys are still active somewhere in the database or whatever.
Importing the old survey's into new format doesn't change anything. I'm totally confused.