Not sure what type of network or computers you’ve got. So I will make the wild assumption that you have minimal complexity.
First you want to shut off the printer and any external attached print server appliance if any. If you don’t they can store the print job and some even report it back as part of print queue –though this is unlikely if you got basic cheap equipment. But it can’t hurt.
Then log into machines as Administrator or an adminstrator type account to do the following. Use a domain Adminstrator account if you have Windows Server with domains. Alternatively try to determine which machine and account produced the ASCII dump print job and logon with that user account on that machine.
Now try deleting the job from the print queue now. Print Queues are normally set to prevent you from deleting the print jobs of others users — unless you are an administrator. Or restarting print spoolers as below.
Restart the print spool service on the machine the job was printed from. If the printer is shared off another computer to which it is directly attached — restart the print spool service there too. The print spooler is restarted from within the Control Panel applet Services. Double click Services icon. Then find Print Spooler in list — typical right click menu option on Print Spooler itself.
If your environment is in fact setup with servers and domains.