COVID-19 infection can indeed be detected via viral RNA testing long after symptom onset, as studies show viral shedding can persist for weeks or months.
The claim is a specific, empirical assertion that COVID-19 can be detected long after symptom onset. Retrieved papers such as systematic reviews on viral shedding (Paper 3) and studies on long-term viral RNA persistence (Paper 10) explicitly support this fact by demonstrating that SARS-CoV-2 RNA is detectable weeks to months after symptoms begin.