Partition disappeared after shrinking

You say it is a "Pentium laptop." However, that cant be accurate, as Windows 10 will not run on a Pentium CPU. I assume the laptop is far newer, but still old. And there lies your problem. Older non-EFI drives cannot have more than 4 primary partitions.

As for recovering your partition, there are many utilities out there that might be able to recover it. You should stop using that computer and remove the drive. Then attach the drive to another computer internally, or by an external method, such as USB. Then you can attempt to recover the partition with one of these utilities. The longer you use the drive with the missing partition, the more likely you are to lose data or the entire partition.

As you say you are trying to install CentOs I assume you will be able to boot another o.s.

I would suggest you to try Parted. It can rescue partitions quite easily. A normal Ubuntu bootable image has parted included. I don't know of CentOs but it is quite reasonable that its installation image includes it too.