Out of the sample of LGRBs detected by the GBM (a band of 8-1000MeV) only about 6.4% were detected by LAT (energies above 100MeV). This has been used to infer about the HE component of GRBs. We show, using stack analysis, that within the bursts detected by the GBM but not by LAT there is clear evidence (statistical significance of 5σ) of HE emission. In addition, this HE fluence continues for a few hundreds of seconds, much after T90. We also develop a new technique for achieving upper limits on the HE fluence of individual bursts. Using it, we achieve tighter limits on the GBM-LAT fluence ratio. For our sample of the 18 most luminous GBM-detected but LAT non-detected bursts we obtain an average fluence ratio of 0.37 for 600 seconds and an average ratio of 0.14 for T90. These ratios can be used to constrain various emission models and in particular rule out SSC models for the prompt emission.