Did you make sure the entry form was updated to show the field?

If I understand what you are trying to do you are creating 2 custom records ReceivalLog and ShippedPackages basically. The relationship is a single ReceivalLog records will have 1->many ShippedPackages.

1. I would start first creating the custom record ReceivalLog record type Customization->Lists,Records&Fields->Record Types then complete the form and save
2. Then Edit the new new record type and add your fields
3. Next repeat steps 1 and 2 for the Shipped Packages record
4. When adding a fields for ShippedPackages be sure to add a field connect back to the RecievalLog in step 1
   1. Type = List/Record
   2. List/Record = Receival Log
   3. Make Sure the checkbox for “Record Is Parent” is checked

That should create your ReceivalLog and many child entries