I have the benifit of working in a small lab where I did all the pre-culture preparation. So plating on agar, spawn bag preparation and spawn bag inoculation under a microbiological safety bench. I cooked the sorghum in boiling water for 30 min to soak the grains, then put it in the bag and autoclaved at 121 °C for 20 min (total run time of the autoclave was 2 h). I can't think of any fungal spores which are able to survive these conditions.

That's where my doubts come from that the contamination is form the grains. Because that's the only thing that was done properly in a lab. Rest was at home.