Over 60% of adults in the UK don't have a Will so it is highly likely you've come across this situation and if you haven't you are very likely too.
When somebody dies, sometimes the next of kin do not know if the deceased left a Will. There are a number of things you can do to find out if the deceased has left a Will:
look in the deceased’s safe / box or drawer of ‘valuable documents’
ask family and friends if they are aware of a Will having been prepared
ask the deceased’s accountant / solicitor / financial advisor / bank – as they may have a copy or they may have helped the deceased to draft up a Will
look at websites like: www.gov.uk/search-will-probate which has a section “Find a will or probate (England and Wales)"
or look at www.citizensadvice.org.uk/relationships/death-and-wills/wills/#h-looking-for-copies-of-a-will-after-someone-dies which has a section “Looking for copies of a will after someone dies”. It also gives details of a commercial organisation that might be able to assist you.