That's some bad luck. Did you have a check engine light / diagnostic trouble code due to glow plug failure prior to this happening?
Were you shown the glow plug? Do you trust the mechanic? FYI there are a couple "travelling mechanics" in this community that know these things very well and can save you a ton of money if you choose to repair it:
https://shop.sasquatchparts.com/installers/The original glow plugs were ceramic-tipped when the CRD rolled off the assembly line. They worked great in cold temps but also had a tendency to crack when they failed, sending shards of ceramic tip into the cylinder, causing devastating engine damage (destroyed cylinder liner, piston, valves, fuel injector, damage to the head, etc.) New longblocks are about $5,000+ last time I checked.
Jeep figured this out at some point and as a result the ceramic tipped glow plugs were discontinued and are no longer available. ALL replacements are now steel glow plugs. (They also happen to not work as well in cold temps compared to the ceramics.)
Bottom line: sounds like your CRD had the original set of ceramic-tipped glow plugs, one of which failed, sending ceramic shards through the #2 cylinder.
You will need a competent mechanic who knows the specifics of the CRD and access to affordable parts (geordi will chime-in soon I'm sure). Good news is, you have access to both through the LOST CRD community.
https://shop.sasquatchparts.com/installers/http://www.idparts.com/http://www.vmdieselspecialist.com/
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Chevy Colorado/GMC Canyon 2.8L Duramax