From Longman Dictionary of Contemporary Englisha blessing in disguisea blessing in disguiseLUCKYsomething that seems to be bad or unlucky at first, but which you later realize is good or lucky → blessing
Examples from the Corpus
a blessing in disguise• But in a way that time lag, though it could be frustrating, was also a blessing in disguise.• Be positive, this could be a blessing in disguise, use the time gained wisely.• The Labour defeat was a disaster, but it might be a blessing in disguise.• The loss of fertilizer proved to be a blessing in disguise. It forced us to use compost, which is better for the soil and crops.• Well, maybe this is a blessing in disguise.• The great cattle freeze of the white winter had been, in retrospect, a blessing in disguise.• The crash was a blessing in disguise for Schwab.• Poor Jonas' death was a blessing in disguise, though one could wish it had happened differently.• Again, one may be forced to the conclusion that his departure was a blessing in disguise for him. 