loose crankshaft pulley

hello - hoping for a bit of advice please if possible.
a local garage changed the timing belt on 200tdi disco 1 for me - this was march and no previous problems of following type
it was fine till yesterday when alternator light came on and car overheated
the crankshaft bolt had come loose and the pulley was turning freely on the crank
from under the car i could turn the pulley freely on the crank with no resistance
i put a fine screwdriver down the keyway slot in the pulley and turned the pulley until i located the place on the crankshaft where the woodruff key should be
this allowed the pulley to move with the crankshaft
when i took the screwdriver out of the slot the pulley stayed 'locked' to the crankshaft and the pulley and crankshaft will turn together - the large bolt has not yet been replaced

my question is - have i moved the woodruff key back into place, will it be safe to lock up the pulley with the bolt, is it likely that there is damage to pulley and/or crank
there doesn't seem to be play on the pulley when trying to move it each way
any advice would be most welcome - thanks

I would take the pulley off andlook at the key before tightening the bolt again!

yes key will hae dislodged, remove pulley and visibly check, pulley will probably be scrap now anyway.

I am surpised it took so long for this to become apparent as the 200tdi is far from a smooth runner and will shake the best done up bolt loose.

I had a similar experience of the crankshaft pulley bolt coming loose after a timing belt change but it didn't take long only a couple of weeks. There was a strange rumbling noise that got louder as revs went up and suddenly went at around 2000 rpm. I checked everything that had been undone during a recent timing belt change and found the crankshaft pulley wheel not sitting vertical. A check of the bolt found it to be loose by half a turn, did a quick tigthen up and that stopped the noise.

Not knowing if this was due to the bolt threads being worn or just needing a tigthen up I went straight back to the guy who did the job. He was good as gold, went straight under the front and set to tightening it up. Not a problem since and that's 18 months now. The engineer did say he'd had this before and only brute force eg club hammer on a strong extension bar seemed to lock the bolt in place.

Threadlock?