The call stack for DROP TEMPORARY TABLE is:

THD::drop_temporary_table()
mysql_rm_table_no_locks()
free_tmp_table_share()
THD::free_tmp_table_share()
THD::rm_temporary_table()
ha_delete_table()

The problem is that free_temp_table_share() is a void function and thus the caller doesn't know if ha_delete_table() failed or not.

How to repeat:
in gdb, put a breakpoint at: maria_delete_table()
Execute in command tool:
create temporary table t1 (a int) engine=aria;
drop temporary table t1;