We present the first measurement of photoproduction of $phi.alt$ mesons in ultra-peripheral Au+Au collisions at a center-of-mass energy of $sqrt(s_N N)$ = 200 GeV using the STAR detector at RHIC. The $phi.alt$ mesons are reconstructed via their decay into $K^+ K^-$ pairs, made possible for the first time due to the added low transverse momentum ($p_perp$) coverage of the STAR iTPC. We report coherent $phi.alt$ photoproduction differential cross sections as functions of transverse momentum ($p_perp$) and rapidity ($y$). We present a comparative analysis with previous STAR measurements of $rho^0$ and $J slash psi$ photoproduction in UPCs. Access to the $phi.alt$ meson, compared to previous measurements of vector mesons ($rho^0$, $J slash psi$), allows us to study the mass dependence of photoproduction processes and probe different aspects of the nuclear gluon distribution. Our results show that the phi meson photoproduction cross section lies between those of $rho^0$ and $J slash psi$, highlighting the transition from soft to hard photoproduction regimes. This measurement provides new constraints on theoretical models of photonuclear interactions and enhances our understanding of the nuclear gluon structure at low $x$.