The word search solution is relatively straightforward, as unusual twists have been foregone in this puzzle. Answers to the clues are listed in ascending order by length, and alphabetically within each length. The leftover letters in the grid spell the message "FOLLOW THE SAME TRAIL AGAIN WHAT THREE WORDS DO YOU GET NOW USE CHRIS SHELDRICK LOCATOR APP." But what trail is there to follow?
Close inspection of the word search grid should establish that most of the words in the are grid connected, while the words which are not connected can be arranged to spell SEVENTEEN CHAINED CONNECTIONS SPELL SECOND SOURCE. Close inspection of the clues reveals that one begins with A, one with B, ..., one with R—none begin with S and the rest begin with T. Alphabetizing the clues gives:
|"C'mon, you expect me to believe that?"||PUH-LEEZE|
|Doorways in the Sand author||ROGER ZELAZNY|
|Emir's coffee-cup holder||ZARF|
|Favorite, at a sports book||SAFE BET|
|Geddy of Rush||LEE|
|Hived off, in British parlance||DIVERTED|
|Investigate for prints||DUST|
|Justification by mathematical example, perhaps||EXISTENCE PROOF|
|Kidder of Pakistani descent featured in Der Koch||JEFF MIRZA|
|Litigant's solicitation during discovery||REQUEST TO ADMIT|
|Musical categorizations found in hymnals||METRICAL INDEXES|
|Name of 2013's Preakness-winning horse||OXBOW|
|Original Blankety Blank host Terry||WOGAN|
|Payette tributary's tributary||DEADWOOD RIVER|
|Regularly consumed foodstuff||DIETARY STAPLE|
|Tarkington satire of first love||SEVENTEEN|
|Tethered (to), in a way||CHAINED|
|Ties to powerful people||CONNECTIONS|
|Time period of unspecified length||SPELL|
|Type of code||SOURCE|
The answers to the six clues that begin with T are (in order): SEVENTEEN CHAINED CONNECTIONS SPELL SECOND SOURCE. (These are also exactly the entries that cross no others.) The other 18 entries form a series of connected words in the word search. Taking the connecting letters in each case, starting with the B used by both SUBHEADING and DIMBULB, spells out BUZZFEEDSFRIXWORD. The word-search grid has the same dimensions as the BuzzFeed crossword for the Friday of the MIT Mystery Hunt (Friday, January 15, 2016).
Looking in the crossword at the 17 positions where the letters BUZZFEEDSFRIXWORD appeared in the word search gives SCRIPT█PILL█MERIT. These three words, when entered into what3words (Chris Sheldrick's locator app), act as geolocation coordinates.
Going to the location specified this way allows the solver to find a geocache with (several copies of) the following 15x16 grid:
Using this to pick out 18 letters from the crossword gives (in order) ANSWERSKYCHASEZONE. Thus, the final answer is SKY CHASE ZONE.
Thanks to Caleb Madison at BuzzFeed for helping make this puzzle happen.