The active ingredient in an Ageless Absorbtion Package is iron. It works by the oxygen chemically reacting with iron in the package to cause rust, and thus removes oxygen from the sealed environment.
Iron can be toxic if eaten in large quantities, but the type of iron present will affect how much your pup actually absorbs and the small amount he may have ingested from one sachet is unlikely to be enough to be truly toxic.
No clinical signs of toxicity are expected in dogs ingesting less than 20 mg/kg of elemental iron. Dogs ingesting between 20 and 60 mg/kg of elemental iron can develop mild clinical signs. If the dog ingests greater than 60 mg/kg of elemental iron, serious clinical signs can develop. An oral dose between 100 and 200 mg/kg is possibly deadly.
For example if your pup is 20 pounds he is 9kgs. If he ingested less than 180mgs (9kgs X 20mgs/kg = 180mgs) of elemental iron he will be fine.
If he ate less than 540mgs of elemental iron then I would expect very mild signs including nausea, vomiting, diarrhea and loss of appetite.
If you can tell me the milligrams of iron in the pill, and the type of iron I can help you figure out how much Patches truly received.
But odds are that with the amount he may have ingested from one partial package he will be fine.
You might see mild stomach upset, as iron can make them nauseous even at nontoxic levels, but that really should be it.