i got a same problem... on my machine i can find following

locate qt|grep -i mysql
/usr/include/qt4/Qt/qsql_mysql.h
/usr/include/qt4/QtSql/QMYSQLDriver
/usr/include/qt4/QtSql/QMYSQLResult
/usr/include/qt4/QtSql/qsql_mysql.h
/usr/lib/qt4/plugins/sqldrivers/libqsqlmysql.so
/usr/share/doc/libqt4-sql-mysql
/usr/share/doc/libqt4-sql-mysql/LGPL_EXCEPTION.txt
/usr/share/doc/libqt4-sql-mysql/changelog.Debian.gz
/usr/share/doc/libqt4-sql-mysql/changelog.gz
/usr/share/doc/libqt4-sql-mysql/copyright
/var/lib/dpkg/info/libqt4-sql-mysql.list
/var/lib/dpkg/info/libqt4-sql-mysql.md5sums

is the /usr/lib/qt4/plugins/sqldrivers/libqsqlmysql.so right library???