User can't find own Tables with Sysadmin role

[harrywartig]

Hi

Hi i have a Database an a SQL User to Access it. My SQL User "appuser" has no Serverroles and is DBO of the Database "dbapp". He is objectowner of all user tables "dbapp.appuser.TableName". Now i've grant the User the sysadmin role. Now he has no access on his own Tables: Statement:

use dbapp
Select * from TableName

if i try:
use dbapp
Select * from appuser.TableName

it Works. --> Why???