There are a few potential reasons why the RFID chip in the dead guy's hand was not blocked from Helix.
One possibility is that the chip was not powered up at the time that Helix was trying to read it. RFID chips rely on a power source (usually a battery) to operate, and if the chip is not powered on, it cannot be read.
Another possibility is that the chip was placed too close to the reader for Helix to be able to properly block it. RFID chips use radio waves to communicate with readers, and the reader must be within a certain range in order to properly receive the signal. If the chip is placed too close to the reader, the reader may not be able to properly block the signal.
Finally, it is also possible that the RFID chip was simply not designed to be blocked by Helix. Some RFID chips are designed to be unblockable, or to have a very high resistance to being blocked. In these cases, even if the chip is powered off or placed too close to the reader, the chip may still be able to be read.