This is easily fixed. They can do it the same way they do every time they think they've got a case against someone, but screw up and realize the prosecution will fail. They just find some other scapegoat and charge them with obstruction of justice. The preeminent example is the Martha Stewart case. The feds were going after Peter Bacanovic for insider trading. When they discovered they didn't the evidence to indict, they looked at all the people they talked to during the investigation and decided Martha Stewart had lied, so they went after her for obstruction.
They can do the same switch in this case. Can't convict a suspect because their phone is encrypted? Charge some high-profile Google or Apple executive with obstruction of justice instead.