When I answered, nobody replied.

Call from something billing itself as "The Clean Planet" (per caller ID).  Most likely some sham environmental group soliciting donations for Al Gore's next project.  I didn't answer and they didn't leave a message, so this number now resides in my blocked caller list.  :-)

The caller ID said Provo, UT, but Utah's area code is 801. Very suspicious.

The caller ID said Provo, Utah, but the Utah area code is 801. Very suspicious

Utah also has 435 and 385 area codes. They surpassed the limit for 801 numbers in about 2007.