Missing P45 & Tax refunds

If an IB issues a Statement Of Earnings in place of a missing P45 after a summer internship (they claim it was mailed to my UK address – but the person I lived with before leaving UK claims to have never received it)—how is the section of the P85 asking about availability of a P45 to be filled? Do I answer in the affirmative to the P85 question regarding the availability of the P45 (as I would be attaching the Statement Of Earnings like it's a P45-equivalent)? OR do I answer that it is unavailable & specify the reason for unavailability as its being missing, while stating that a Statement Of Earnings is attached to the application in place of a P45? I ask because the usual SAMPLE-reasons for P45-unavailability stated by HMRC include reasons completely unrelated to a missing P45—such as—an employer being unable to issue or being a Crown Servant.
Is it probable that HMRC would deny a tax refund application on the basis of a missing P45?

PS: Is it common for a non–UK/EU National who only came to UK for summer internships – & left immediately afterwards – to claim a refund of National Insurance deductions that were taken during the internship?