Losing a highly skilled migrant role puts residence status on a countdown, and the length of that countdown changed recently, so guidance written a year or two ago now quotes the wrong number. Permit expiry dates can also cut the window shorter than the headline rule suggests.
It depends on how long you've held the permit, and this changed in your favour recently. If you've held your HSM permit continuously for at least two years, you now get six months from your last day of employment to find a new IND-recognised sponsor at a qualifying salary — up from the old flat three-month rule. Under two years on the permit, and the original three months still applies. Either way, the search period can't run past your current permit's expiry date, so if your permit was due to expire in ten weeks when you lost your job, that's your real deadline regardless of the six-month allowance. You're expected to notify the IND that you're between jobs, and any new employer has to be a recognised sponsor offering a salary that clears the relevant HSM threshold at the time you apply — not the threshold from when you were first hired. Given this is a fairly recent change, it's worth confirming your exact situation with the IND or an immigration lawyer rather than assuming which rule applies to you.