TPOab being negative for autoimmune thyroiditis (Hashimoto's) isn't conclusive. Some people are negative for TPOab but positive for thyroglobulin antibodies which NHS doesn't often test. The fluctuation in your friend's TSH levels is indicative of an autoimmune flare up.
A virus can elevate TSH which is why protocols suggest retesting up to 3 months after the first abnormal TSH. TSH 2.68 indicates the thyroid gland is beginning to struggle but NHS won't usually diagnose hypothyroidism until TSH is >5.6 or FT4 <8.0.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.