Can silicon temperature sensor (e.g. KTY84)'s polarity be inferred if it's inaccesible - polarity band cannot be visually checked?
Here is a manual for another (polarized KTY device) that gives a little more information about it:
https://carbonbrushsolution.com/wp-content/pdf_datablad/datablad-kty-84.eng.pdf
 On the first page is the most relevant information:
"Colour/Connection
• KTY 84 is a semi-conductor where one end is an
 anode (plus) and the other a cathode (minus). A wide
 range of colour combinations is available on the market.
 The sensor’s ring marking can be checked to ensure
 the wiring is correct. The ring is the cathode side. It is
 therefore of the utmost importance to know what the
 wire colour codes are for the anode and cathode in
 those cases where the sensor is embedded. To verify
 the polarity by way of measurement requires heating
 of the sensor to see when the resistance follows the
 temperature curve as shown in the data sheet.

 So, you have to heat the sensor in order to test its polarity.

 If you are able to see the sensor's wire colors, you might be able to get the polarity right, but this depends on the manufacturer and possibly custom-specified color-coding. I have found one below:
https://www.ephy-mess.de/fileadmin/Daten/Downloads/Produktkataloge_EN/EPHY-MESS_GmbH_Catalog_Semiconductor_thermistors.pdf
 on page 13 there is a color-code mentioned for a KTY84 sensor:
"Colour code¹
(+) = yellow
(-) = green
¹Colour code of EPHY-MESS KTY84-1xx sensors"  

So, there you have it, you either have to heat the sensor up to test it with a multimeter, or you could check the color codes used by the manufacturer. Hopefully, this is the color-coding used in your case.  

P.S.: Since they are non-symmetrical only above 150°C, the polarity might not matter if you only need it up to that temperature, as you must have figured that out already.