Something similar happened to me while buying a domain for my company abtesting.ai using namecheap.
I was trying to decide between abtesting.ai and abtest.ai (both were free while checking). Luckily I decided to go with abtesting.ai and got the domain right away. A week after that I decided that it may be a good idea to buy abtest.ai anyway so someone else wouldn't try to impersonate our company. However, when I checked again the domain was already sold...