Compression is actually a mathematical field that's fairly well explored, and this isn't compression. There are theoretical limits on how much you can compress data, so the data is always somewhere, either in the dictionary or the input. Trained models like these are gigantic, so even if it was perfect recall the ratio still wouldn't be good. Lossy "compression" is another issue entirely, more of an engineering problem of determining how much data you can throw out while making acceptable compromises.