If you have a lot of time on your hands, you could use inurl:keyword but that matches in the entire URL so there is likely to be a lot of noise.
Not all of the activity that’s saved to your account shows up in My Activity. For example, if you’ve turned on Location History, that activity is saved to your Maps Timeline instead.
What happens to deleted activity
When you delete items from My Activity, they are permanently deleted from your Google Account. However, Google may keep service-related information about your account, like which Google products you used and when, to prevent spam and abuse and to improve our services.
Learn more about the information we collect and why.