This reproduces with the following code:

let conn = ::rusqlite::Connection::open_in_memory().unwrap();
conn.execute(r#"
    CREATE TABLE t1 ( id integer primary key, f1 text );
    CREATE TABLE t2 ( id integer primary key, f1 text );
"#, &[]).unwrap();
conn.execute("SELECT * FROM t2;", &[]).unwrap();

The first execute succeeds, and the table t1 is created and is accessible. However, the table t2 is not, meaning the second statement was actually never executed. So the second execute fails with SqliteFailure(Error { code: Unknown, extended_code: 1 }, Some("no such table: t2"))

The correct outcome would be to either execute both statements or return an error when asked to do so.