DS18B20: Invalid device type returned?

May not be specific to the Particle devices, but calling getChipType is sometimes throwing invalid types (rather than 0, meaning Unknown) on pins where no Dallas device exists. Other times, it throws invalid types even for a validly connected Dallas device. Pulling power and reconnecting, sometimes more than once, fixes this.

I’ll be trying some other of the same model temperature sensor to see if this is a common issue.

Anyone else seeing this issue?

What library are you using?
The DS18B20 library gives you back the first [0] byte of the ROM number which should be one of 0x10, 0x22 or 0x28 anything else is considered unknown.
Now with a floating pin you can get any combination of ghost bits which will most the time not fit the pattern - which is good - but sometimes you may even get a false positive which wouldn’t be that good either.
The OneWire protocol can be a bit finicky hence CRC checks are always advisable.