01 transmission help please!!
 

I have a 01 chevy s10 and in the process of a clutch slave replacement a friend removed a bolt going straight into the transmission right where the bell housing meets the tranny.it's a long half thread bolt.the issue is now the bolt won't go back in and clearly something is blocking it now.I can't figure out for the life of me what it is or it's purpose or how to get back in, please help!!I have pics also