If I forgot to turn on find my iPhone is there any other way to find it

No there isn't, except to physically look for it. Find My iPhone has to be activated prior to the loss of the device to be able to use if for tracking. You can always verify if you activated it or not by going to www.icloud.com and signing in with your iCloud ID and password, and see if the device shows on the list.

Physically search for it, or put notices around where you lost it, or if applicable, contact the people running the place where it was lost and/or its wireless carrier(this is only possible for devices with a SIM card.)

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