On this site we can not provide medical advice to anyone. However, as with any disease, you should monitor for symptoms and if concerned visit a health professional for diagnosis and treatment.
However, I don't think your core question is personal medical advice - you are asking about the sensitivity of the tests and whether someone could test negative on a test but still be infectious.
I'm assuming that you and the others in your group were using Rapid Antigen Tests (RATs, AKA Lateral Flow Assays [LFA]).
If so, this infographic from Dankova et al. might be of some use to you:
In this picture, you can see the dotted line for the viral infection going though 3 main phases of infection, incubation (grey), infectious (pink/peach) and post-infectious (green). Note that the timing of the infection is an idealized model, and not necessarily what is experienced in real-life. Most people will have an infectious process with roughly the same timing, but for some the phases may be longer or shorter. It is entirely possible to have a very short incubation, long infectious and long post-infectious phases.
On the X-axis there is a box showing the relative sensitivities for the RAT/LFA (red) and PCR tests (cyan). As you can see the RAT/LFA have a fairly short window in which they will detect the virus, and that this window does not completely overlap the infectious phase, missing the early part of this phase.
So, it is possible that transmission can occur from a person who has tested negative by a RAT/LFA, but this is less likely from a qPCR test.
- Dankova, Z.; Novakova, E.; Skerenova, M.; Holubekova, V.; Lucansky,
V.; Dvorska, D.; Brany, D.; Kolkova, Z.; Strnadel, J.; Mersakova, S.;
Janikova, K.; Samec, M.; Pokusa, M.; Petras, M.; Sarlinova, M.;
Kasubova, I.; Loderer, D.; Sadlonova, V.; Kompanikova, J.; Kotlebova,
N.; Kompanikova, A.; Hrnciarova, M.; Stanclova, A.; Antosova, M.;
Dzian, A.; Nosal, V.; Kocan, I.; Murgas, D.; Krkoska, D.; Calkovska,
A.; Halasova, E. Comparison of SARS-CoV-2 Detection by Rapid Antigen
and by Three Commercial RT-qPCR Tests: A Study from Martin University
Hospital in Slovakia. Int. J. Environ. Res. Public Health 2021, 18,
Other articles you might be interested in:
- Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 Transmission From People Without COVID-19 Symptoms. JAMA Netw Open. 2021;4(1):e2035057. doi:10.1001/jamanetworkopen.2020.35057
- Krumkamp R, Kreuels B, Jaeger VK, May J, Mikolajczyk R, Karch A. Negative SARS-CoV-2 PCR or rapid antigen test result and the subsequent risk of being infectious: a mathematical simulation study. BMC Med Res Methodol. 2021 Aug 10;21(1):165. doi: 10.1186/s12874-021-01361-3. PMID: 34376152; PMCID: PMC8353420.