Presuming you are not on a server with regenerating POIs, you can add a salvage core to the shipyard and use the F4 menu to see check all of the (non-alien containers) to see if there are any you missed.

Salvage each container you loot along the way if you can, it will make identifying any missed a lot easier. Also, if you salvage all the cargo containers do the devices lists them at 0 and then check the CPU statistics, if there are any cargo containers remaining in that list it means there are alien containers you did miss (quantum containers should still be listed in the F4 menu if they exist though).