stem flat???

I checked on my plants and one of my smallest ones had fallen over so i propped it back up and then its condition kept declining and it died but down near the soil the stem went from round to flat to round it was flat for about 1/4 inch what could cause this?????:wtf:

was it flat where it bent over and the stem was pinched

if so the stress from being layed over helped cause it. theres a possibility it could have some disease like a stem rot to help create the conditions