LC-MS stands for liquid chromatography mass spectrometry and, therefore, is implied that you are using an HPLC or UHPLC technique.
In response of your question, to really confirm the presence of a compound in an LCMS analysis you need to have information of a reference compound (pure standard of your analyte of interest).
Once you have this information, you compare the retention time and ion ratios to confirm the identity of your analyte.
You, even, do not need employment in LC in order not only to validate your analyte, but also to determine its exact 3D molecular and electronic structures. Particularly, there can be determined tautomeric forms of the analyte, which are frequently found in phytocompounds.
Please, concentrate on our own authored (to me and my co-author as the references show, below) innovative stochastic dynamic mass spectrometric theory and model equations (refs. [1,2]), which are capable of quantify and determine 3D structurally analytes mass spectrometrically.
[1] B. Ivanova, M. Spiteller, Stochastic Dynamic Electrospray Ionization Mass Spectrometric Quantitative Analysis of Metronidazole in Human Urine, 2022, Analytical Chemistry Letters 12(3):322-34
[2] B. Ivanova, M. Spiteller, Chapter 1. Mass Spectrometric and Quantum Chemical Treatments of Molecular and Ionic Interactions of a Flavonoid-O-Glycoside – A Stochastic Dynamic Approach, J. Taylor (Ed.) In: Advances in Chemistry Research, Vol. 74, NOVA Science Publishers, New York, 2022, pp. 1-126.