Lot tracking means your inventory system knows which manufactured batch every unit in the building came from, and can produce that answer without anyone opening a fridge. Most laboratory inventories track catalogue items instead — quantity of a named compound at a named strength — which is adequate for reordering and useless for an investigation. The gap only becomes visible on the day you need it.
Track units, not quantities
A row that reads "BPC-157 10 mg, quantity 6" cannot tell you whether those six vials came from one batch or three, when each arrived, or which analytical record applies to which. Model the unit as the tracked object and carry the lot identifier as a required field on it.
The failure mode this prevents is the untraceable pooled row. Once two batches are merged into one quantity, no subsequent record-keeping separates them, and a question about a single vial can only be answered about the whole shelf.
Make the lot identifier a required, verified field
If the lot field can be left blank, it will be blank on the entries that matter. Make it mandatory at goods-in, and require that the string is transcribed from the vial rather than from the invoice, because the invoice is a commercial document and the vial is the physical truth.
Verify the string at the same moment you record it. Entering it into batch verification while the box is open catches transposition immediately, when the carton is still in front of you. The batch verification guide