I actually found that you can find the SPID of the of a linked server call using master..sysprocesses on the local server under the waitresource field, INVENTORY is the alias to the linked server in this case and SPID 139 is remote SPID:

spidkpidblockedwaittypewaittimelastwaittypewaitresource

53842800x006D78 OLEDB INVENTORY (SPID=139)