The most likely cause is a major light leak in the disposable camera, not normal lab processing. The clue is that the orange/bright leak appears in the same place on many frames, including the negatives. If the lab had caused the fogging during development, it usually wouldn’t line up consistently frame to frame.

The black or missing-looking frames were probably badly underexposed, and the lab may have printed/scanned based on the brightest leaked area, making the actual image look very dark or blank. A lab might be able to rescan or reprint some frames to recover a little more detail, but any blown-out leaked area is permanently damaged.

As for a refund: proving exactly whether it was camera, lab, or handling fault is usually difficult and not worth a big fight. The practical step is to go back to the store where you bought the disposable camera, show the negatives/prints, and ask for a replacement or refund if you still have the receipt.